revert between 56095 -> 55830 in arch
[AROS.git] / workbench / libs / png / pngread.c
blobf8e762196eb1ad9ab19a6758be9eab59dd63b796
2 /* pngread.c - read a PNG file
4 * Copyright (c) 2018 Cosmin Truta
5 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
6 * Copyright (c) 1996-1997 Andreas Dilger
7 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
13 * This file contains routines that an application calls directly to
14 * read a PNG file or stream.
17 #include "pngpriv.h"
18 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
19 # include <errno.h>
20 #endif
22 #ifdef PNG_READ_SUPPORTED
24 /* Create a PNG structure for reading, and allocate any memory needed. */
25 PNG_FUNCTION(png_structp,PNGAPI
26 png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
27 png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
29 #ifndef PNG_USER_MEM_SUPPORTED
30 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
31 error_fn, warn_fn, NULL, NULL, NULL);
32 #else
33 return png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
34 warn_fn, NULL, NULL, NULL);
37 /* Alternate create PNG structure for reading, and allocate any memory
38 * needed.
40 PNG_FUNCTION(png_structp,PNGAPI
41 png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
42 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
43 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
45 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
46 error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
47 #endif /* USER_MEM */
49 if (png_ptr != NULL)
51 png_ptr->mode = PNG_IS_READ_STRUCT;
53 /* Added in libpng-1.6.0; this can be used to detect a read structure if
54 * required (it will be zero in a write structure.)
56 # ifdef PNG_SEQUENTIAL_READ_SUPPORTED
57 png_ptr->IDAT_read_size = PNG_IDAT_READ_SIZE;
58 # endif
60 # ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED
61 png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
63 /* In stable builds only warn if an application error can be completely
64 * handled.
66 # if PNG_RELEASE_BUILD
67 png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
68 # endif
69 # endif
71 /* TODO: delay this, it can be done in png_init_io (if the app doesn't
72 * do it itself) avoiding setting the default function if it is not
73 * required.
75 png_set_read_fn(png_ptr, NULL, NULL);
78 return png_ptr;
82 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
83 /* Read the information before the actual image data. This has been
84 * changed in v0.90 to allow reading a file that already has the magic
85 * bytes read from the stream. You can tell libpng how many bytes have
86 * been read from the beginning of the stream (up to the maximum of 8)
87 * via png_set_sig_bytes(), and we will only check the remaining bytes
88 * here. The application can then have access to the signature bytes we
89 * read if it is determined that this isn't a valid PNG file.
91 void PNGAPI
92 png_read_info(png_structrp png_ptr, png_inforp info_ptr)
94 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
95 int keep;
96 #endif
98 png_debug(1, "in png_read_info");
100 if (png_ptr == NULL || info_ptr == NULL)
101 return;
103 /* Read and check the PNG file signature. */
104 png_read_sig(png_ptr, info_ptr);
106 for (;;)
108 png_uint_32 length = png_read_chunk_header(png_ptr);
109 png_uint_32 chunk_name = png_ptr->chunk_name;
111 /* IDAT logic needs to happen here to simplify getting the two flags
112 * right.
114 if (chunk_name == png_IDAT)
116 if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
117 png_chunk_error(png_ptr, "Missing IHDR before IDAT");
119 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
120 (png_ptr->mode & PNG_HAVE_PLTE) == 0)
121 png_chunk_error(png_ptr, "Missing PLTE before IDAT");
123 else if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)
124 png_chunk_benign_error(png_ptr, "Too many IDATs found");
126 png_ptr->mode |= PNG_HAVE_IDAT;
129 else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
131 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
132 png_ptr->mode |= PNG_AFTER_IDAT;
135 /* This should be a binary subdivision search or a hash for
136 * matching the chunk name rather than a linear search.
138 if (chunk_name == png_IHDR)
139 png_handle_IHDR(png_ptr, info_ptr, length);
141 else if (chunk_name == png_IEND)
142 png_handle_IEND(png_ptr, info_ptr, length);
144 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
145 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
147 png_handle_unknown(png_ptr, info_ptr, length, keep);
149 if (chunk_name == png_PLTE)
150 png_ptr->mode |= PNG_HAVE_PLTE;
152 else if (chunk_name == png_IDAT)
154 png_ptr->idat_size = 0; /* It has been consumed */
155 break;
158 #endif
159 else if (chunk_name == png_PLTE)
160 png_handle_PLTE(png_ptr, info_ptr, length);
162 else if (chunk_name == png_IDAT)
164 png_ptr->idat_size = length;
165 break;
168 #ifdef PNG_READ_bKGD_SUPPORTED
169 else if (chunk_name == png_bKGD)
170 png_handle_bKGD(png_ptr, info_ptr, length);
171 #endif
173 #ifdef PNG_READ_cHRM_SUPPORTED
174 else if (chunk_name == png_cHRM)
175 png_handle_cHRM(png_ptr, info_ptr, length);
176 #endif
178 #ifdef PNG_READ_eXIf_SUPPORTED
179 else if (chunk_name == png_eXIf)
180 png_handle_eXIf(png_ptr, info_ptr, length);
181 #endif
183 #ifdef PNG_READ_gAMA_SUPPORTED
184 else if (chunk_name == png_gAMA)
185 png_handle_gAMA(png_ptr, info_ptr, length);
186 #endif
188 #ifdef PNG_READ_hIST_SUPPORTED
189 else if (chunk_name == png_hIST)
190 png_handle_hIST(png_ptr, info_ptr, length);
191 #endif
193 #ifdef PNG_READ_oFFs_SUPPORTED
194 else if (chunk_name == png_oFFs)
195 png_handle_oFFs(png_ptr, info_ptr, length);
196 #endif
198 #ifdef PNG_READ_pCAL_SUPPORTED
199 else if (chunk_name == png_pCAL)
200 png_handle_pCAL(png_ptr, info_ptr, length);
201 #endif
203 #ifdef PNG_READ_sCAL_SUPPORTED
204 else if (chunk_name == png_sCAL)
205 png_handle_sCAL(png_ptr, info_ptr, length);
206 #endif
208 #ifdef PNG_READ_pHYs_SUPPORTED
209 else if (chunk_name == png_pHYs)
210 png_handle_pHYs(png_ptr, info_ptr, length);
211 #endif
213 #ifdef PNG_READ_sBIT_SUPPORTED
214 else if (chunk_name == png_sBIT)
215 png_handle_sBIT(png_ptr, info_ptr, length);
216 #endif
218 #ifdef PNG_READ_sRGB_SUPPORTED
219 else if (chunk_name == png_sRGB)
220 png_handle_sRGB(png_ptr, info_ptr, length);
221 #endif
223 #ifdef PNG_READ_iCCP_SUPPORTED
224 else if (chunk_name == png_iCCP)
225 png_handle_iCCP(png_ptr, info_ptr, length);
226 #endif
228 #ifdef PNG_READ_sPLT_SUPPORTED
229 else if (chunk_name == png_sPLT)
230 png_handle_sPLT(png_ptr, info_ptr, length);
231 #endif
233 #ifdef PNG_READ_tEXt_SUPPORTED
234 else if (chunk_name == png_tEXt)
235 png_handle_tEXt(png_ptr, info_ptr, length);
236 #endif
238 #ifdef PNG_READ_tIME_SUPPORTED
239 else if (chunk_name == png_tIME)
240 png_handle_tIME(png_ptr, info_ptr, length);
241 #endif
243 #ifdef PNG_READ_tRNS_SUPPORTED
244 else if (chunk_name == png_tRNS)
245 png_handle_tRNS(png_ptr, info_ptr, length);
246 #endif
248 #ifdef PNG_READ_zTXt_SUPPORTED
249 else if (chunk_name == png_zTXt)
250 png_handle_zTXt(png_ptr, info_ptr, length);
251 #endif
253 #ifdef PNG_READ_iTXt_SUPPORTED
254 else if (chunk_name == png_iTXt)
255 png_handle_iTXt(png_ptr, info_ptr, length);
256 #endif
258 else
259 png_handle_unknown(png_ptr, info_ptr, length,
260 PNG_HANDLE_CHUNK_AS_DEFAULT);
263 #endif /* SEQUENTIAL_READ */
265 /* Optional call to update the users info_ptr structure */
266 void PNGAPI
267 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
269 png_debug(1, "in png_read_update_info");
271 if (png_ptr != NULL)
273 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
275 png_read_start_row(png_ptr);
277 # ifdef PNG_READ_TRANSFORMS_SUPPORTED
278 png_read_transform_info(png_ptr, info_ptr);
279 # else
280 PNG_UNUSED(info_ptr)
281 # endif
284 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
285 else
286 png_app_error(png_ptr,
287 "png_read_update_info/png_start_read_image: duplicate call");
291 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
292 /* Initialize palette, background, etc, after transformations
293 * are set, but before any reading takes place. This allows
294 * the user to obtain a gamma-corrected palette, for example.
295 * If the user doesn't call this, we will do it ourselves.
297 void PNGAPI
298 png_start_read_image(png_structrp png_ptr)
300 png_debug(1, "in png_start_read_image");
302 if (png_ptr != NULL)
304 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
305 png_read_start_row(png_ptr);
307 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
308 else
309 png_app_error(png_ptr,
310 "png_start_read_image/png_read_update_info: duplicate call");
313 #endif /* SEQUENTIAL_READ */
315 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
316 #ifdef PNG_MNG_FEATURES_SUPPORTED
317 /* Undoes intrapixel differencing,
318 * NOTE: this is apparently only supported in the 'sequential' reader.
320 static void
321 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
323 png_debug(1, "in png_do_read_intrapixel");
325 if (
326 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
328 int bytes_per_pixel;
329 png_uint_32 row_width = row_info->width;
331 if (row_info->bit_depth == 8)
333 png_bytep rp;
334 png_uint_32 i;
336 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
337 bytes_per_pixel = 3;
339 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
340 bytes_per_pixel = 4;
342 else
343 return;
345 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
347 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
348 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
351 else if (row_info->bit_depth == 16)
353 png_bytep rp;
354 png_uint_32 i;
356 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
357 bytes_per_pixel = 6;
359 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
360 bytes_per_pixel = 8;
362 else
363 return;
365 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
367 png_uint_32 s0 = (png_uint_32)(*(rp ) << 8) | *(rp + 1);
368 png_uint_32 s1 = (png_uint_32)(*(rp + 2) << 8) | *(rp + 3);
369 png_uint_32 s2 = (png_uint_32)(*(rp + 4) << 8) | *(rp + 5);
370 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
371 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
372 *(rp ) = (png_byte)((red >> 8) & 0xff);
373 *(rp + 1) = (png_byte)(red & 0xff);
374 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
375 *(rp + 5) = (png_byte)(blue & 0xff);
380 #endif /* MNG_FEATURES */
382 void PNGAPI
383 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
385 png_row_info row_info;
387 if (png_ptr == NULL)
388 return;
390 png_debug2(1, "in png_read_row (row %lu, pass %d)",
391 (unsigned long)png_ptr->row_number, png_ptr->pass);
393 /* png_read_start_row sets the information (in particular iwidth) for this
394 * interlace pass.
396 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
397 png_read_start_row(png_ptr);
399 /* 1.5.6: row_info moved out of png_struct to a local here. */
400 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
401 row_info.color_type = png_ptr->color_type;
402 row_info.bit_depth = png_ptr->bit_depth;
403 row_info.channels = png_ptr->channels;
404 row_info.pixel_depth = png_ptr->pixel_depth;
405 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
407 #ifdef PNG_WARNINGS_SUPPORTED
408 if (png_ptr->row_number == 0 && png_ptr->pass == 0)
410 /* Check for transforms that have been set but were defined out */
411 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
412 if ((png_ptr->transformations & PNG_INVERT_MONO) != 0)
413 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
414 #endif
416 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
417 if ((png_ptr->transformations & PNG_FILLER) != 0)
418 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
419 #endif
421 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
422 !defined(PNG_READ_PACKSWAP_SUPPORTED)
423 if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
424 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
425 #endif
427 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
428 if ((png_ptr->transformations & PNG_PACK) != 0)
429 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
430 #endif
432 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
433 if ((png_ptr->transformations & PNG_SHIFT) != 0)
434 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
435 #endif
437 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
438 if ((png_ptr->transformations & PNG_BGR) != 0)
439 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
440 #endif
442 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
443 if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0)
444 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
445 #endif
447 #endif /* WARNINGS */
449 #ifdef PNG_READ_INTERLACING_SUPPORTED
450 /* If interlaced and we do not need a new row, combine row and return.
451 * Notice that the pixels we have from previous rows have been transformed
452 * already; we can only combine like with like (transformed or
453 * untransformed) and, because of the libpng API for interlaced images, this
454 * means we must transform before de-interlacing.
456 if (png_ptr->interlaced != 0 &&
457 (png_ptr->transformations & PNG_INTERLACE) != 0)
459 switch (png_ptr->pass)
461 case 0:
462 if (png_ptr->row_number & 0x07)
464 if (dsp_row != NULL)
465 png_combine_row(png_ptr, dsp_row, 1/*display*/);
466 png_read_finish_row(png_ptr);
467 return;
469 break;
471 case 1:
472 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
474 if (dsp_row != NULL)
475 png_combine_row(png_ptr, dsp_row, 1/*display*/);
477 png_read_finish_row(png_ptr);
478 return;
480 break;
482 case 2:
483 if ((png_ptr->row_number & 0x07) != 4)
485 if (dsp_row != NULL && (png_ptr->row_number & 4))
486 png_combine_row(png_ptr, dsp_row, 1/*display*/);
488 png_read_finish_row(png_ptr);
489 return;
491 break;
493 case 3:
494 if ((png_ptr->row_number & 3) || png_ptr->width < 3)
496 if (dsp_row != NULL)
497 png_combine_row(png_ptr, dsp_row, 1/*display*/);
499 png_read_finish_row(png_ptr);
500 return;
502 break;
504 case 4:
505 if ((png_ptr->row_number & 3) != 2)
507 if (dsp_row != NULL && (png_ptr->row_number & 2))
508 png_combine_row(png_ptr, dsp_row, 1/*display*/);
510 png_read_finish_row(png_ptr);
511 return;
513 break;
515 case 5:
516 if ((png_ptr->row_number & 1) || png_ptr->width < 2)
518 if (dsp_row != NULL)
519 png_combine_row(png_ptr, dsp_row, 1/*display*/);
521 png_read_finish_row(png_ptr);
522 return;
524 break;
526 default:
527 case 6:
528 if ((png_ptr->row_number & 1) == 0)
530 png_read_finish_row(png_ptr);
531 return;
533 break;
536 #endif
538 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0)
539 png_error(png_ptr, "Invalid attempt to read row data");
541 /* Fill the row with IDAT data: */
542 png_ptr->row_buf[0]=255; /* to force error if no data was found */
543 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
545 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
547 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
548 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
549 png_ptr->prev_row + 1, png_ptr->row_buf[0]);
550 else
551 png_error(png_ptr, "bad adaptive filter value");
554 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
555 * 1.5.6, while the buffer really is this big in current versions of libpng
556 * it may not be in the future, so this was changed just to copy the
557 * interlaced count:
559 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
561 #ifdef PNG_MNG_FEATURES_SUPPORTED
562 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
563 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
565 /* Intrapixel differencing */
566 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
568 #endif
570 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
571 if (png_ptr->transformations)
572 png_do_read_transformations(png_ptr, &row_info);
573 #endif
575 /* The transformed pixel depth should match the depth now in row_info. */
576 if (png_ptr->transformed_pixel_depth == 0)
578 png_ptr->transformed_pixel_depth = row_info.pixel_depth;
579 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
580 png_error(png_ptr, "sequential row overflow");
583 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
584 png_error(png_ptr, "internal sequential row size calculation error");
586 #ifdef PNG_READ_INTERLACING_SUPPORTED
587 /* Expand interlaced rows to full size */
588 if (png_ptr->interlaced != 0 &&
589 (png_ptr->transformations & PNG_INTERLACE) != 0)
591 if (png_ptr->pass < 6)
592 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
593 png_ptr->transformations);
595 if (dsp_row != NULL)
596 png_combine_row(png_ptr, dsp_row, 1/*display*/);
598 if (row != NULL)
599 png_combine_row(png_ptr, row, 0/*row*/);
602 else
603 #endif
605 if (row != NULL)
606 png_combine_row(png_ptr, row, -1/*ignored*/);
608 if (dsp_row != NULL)
609 png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
611 png_read_finish_row(png_ptr);
613 if (png_ptr->read_row_fn != NULL)
614 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
617 #endif /* SEQUENTIAL_READ */
619 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
620 /* Read one or more rows of image data. If the image is interlaced,
621 * and png_set_interlace_handling() has been called, the rows need to
622 * contain the contents of the rows from the previous pass. If the
623 * image has alpha or transparency, and png_handle_alpha()[*] has been
624 * called, the rows contents must be initialized to the contents of the
625 * screen.
627 * "row" holds the actual image, and pixels are placed in it
628 * as they arrive. If the image is displayed after each pass, it will
629 * appear to "sparkle" in. "display_row" can be used to display a
630 * "chunky" progressive image, with finer detail added as it becomes
631 * available. If you do not want this "chunky" display, you may pass
632 * NULL for display_row. If you do not want the sparkle display, and
633 * you have not called png_handle_alpha(), you may pass NULL for rows.
634 * If you have called png_handle_alpha(), and the image has either an
635 * alpha channel or a transparency chunk, you must provide a buffer for
636 * rows. In this case, you do not have to provide a display_row buffer
637 * also, but you may. If the image is not interlaced, or if you have
638 * not called png_set_interlace_handling(), the display_row buffer will
639 * be ignored, so pass NULL to it.
641 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
644 void PNGAPI
645 png_read_rows(png_structrp png_ptr, png_bytepp row,
646 png_bytepp display_row, png_uint_32 num_rows)
648 png_uint_32 i;
649 png_bytepp rp;
650 png_bytepp dp;
652 png_debug(1, "in png_read_rows");
654 if (png_ptr == NULL)
655 return;
657 rp = row;
658 dp = display_row;
659 if (rp != NULL && dp != NULL)
660 for (i = 0; i < num_rows; i++)
662 png_bytep rptr = *rp++;
663 png_bytep dptr = *dp++;
665 png_read_row(png_ptr, rptr, dptr);
668 else if (rp != NULL)
669 for (i = 0; i < num_rows; i++)
671 png_bytep rptr = *rp;
672 png_read_row(png_ptr, rptr, NULL);
673 rp++;
676 else if (dp != NULL)
677 for (i = 0; i < num_rows; i++)
679 png_bytep dptr = *dp;
680 png_read_row(png_ptr, NULL, dptr);
681 dp++;
684 #endif /* SEQUENTIAL_READ */
686 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
687 /* Read the entire image. If the image has an alpha channel or a tRNS
688 * chunk, and you have called png_handle_alpha()[*], you will need to
689 * initialize the image to the current image that PNG will be overlaying.
690 * We set the num_rows again here, in case it was incorrectly set in
691 * png_read_start_row() by a call to png_read_update_info() or
692 * png_start_read_image() if png_set_interlace_handling() wasn't called
693 * prior to either of these functions like it should have been. You can
694 * only call this function once. If you desire to have an image for
695 * each pass of a interlaced image, use png_read_rows() instead.
697 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
699 void PNGAPI
700 png_read_image(png_structrp png_ptr, png_bytepp image)
702 png_uint_32 i, image_height;
703 int pass, j;
704 png_bytepp rp;
706 png_debug(1, "in png_read_image");
708 if (png_ptr == NULL)
709 return;
711 #ifdef PNG_READ_INTERLACING_SUPPORTED
712 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
714 pass = png_set_interlace_handling(png_ptr);
715 /* And make sure transforms are initialized. */
716 png_start_read_image(png_ptr);
718 else
720 if (png_ptr->interlaced != 0 &&
721 (png_ptr->transformations & PNG_INTERLACE) == 0)
723 /* Caller called png_start_read_image or png_read_update_info without
724 * first turning on the PNG_INTERLACE transform. We can fix this here,
725 * but the caller should do it!
727 png_warning(png_ptr, "Interlace handling should be turned on when "
728 "using png_read_image");
729 /* Make sure this is set correctly */
730 png_ptr->num_rows = png_ptr->height;
733 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
734 * the above error case.
736 pass = png_set_interlace_handling(png_ptr);
738 #else
739 if (png_ptr->interlaced)
740 png_error(png_ptr,
741 "Cannot read interlaced image -- interlace handler disabled");
743 pass = 1;
744 #endif
746 image_height=png_ptr->height;
748 for (j = 0; j < pass; j++)
750 rp = image;
751 for (i = 0; i < image_height; i++)
753 png_read_row(png_ptr, *rp, NULL);
754 rp++;
758 #endif /* SEQUENTIAL_READ */
760 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
761 /* Read the end of the PNG file. Will not read past the end of the
762 * file, will verify the end is accurate, and will read any comments
763 * or time information at the end of the file, if info is not NULL.
765 void PNGAPI
766 png_read_end(png_structrp png_ptr, png_inforp info_ptr)
768 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
769 int keep;
770 #endif
772 png_debug(1, "in png_read_end");
774 if (png_ptr == NULL)
775 return;
777 /* If png_read_end is called in the middle of reading the rows there may
778 * still be pending IDAT data and an owned zstream. Deal with this here.
780 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
781 if (png_chunk_unknown_handling(png_ptr, png_IDAT) == 0)
782 #endif
783 png_read_finish_IDAT(png_ptr);
785 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
786 /* Report invalid palette index; added at libng-1.5.10 */
787 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
788 png_ptr->num_palette_max > png_ptr->num_palette)
789 png_benign_error(png_ptr, "Read palette index exceeding num_palette");
790 #endif
794 png_uint_32 length = png_read_chunk_header(png_ptr);
795 png_uint_32 chunk_name = png_ptr->chunk_name;
797 if (chunk_name != png_IDAT)
798 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
800 if (chunk_name == png_IEND)
801 png_handle_IEND(png_ptr, info_ptr, length);
803 else if (chunk_name == png_IHDR)
804 png_handle_IHDR(png_ptr, info_ptr, length);
806 else if (info_ptr == NULL)
807 png_crc_finish(png_ptr, length);
809 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
810 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
812 if (chunk_name == png_IDAT)
814 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
815 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
816 png_benign_error(png_ptr, ".Too many IDATs found");
818 png_handle_unknown(png_ptr, info_ptr, length, keep);
819 if (chunk_name == png_PLTE)
820 png_ptr->mode |= PNG_HAVE_PLTE;
822 #endif
824 else if (chunk_name == png_IDAT)
826 /* Zero length IDATs are legal after the last IDAT has been
827 * read, but not after other chunks have been read. 1.6 does not
828 * always read all the deflate data; specifically it cannot be relied
829 * upon to read the Adler32 at the end. If it doesn't ignore IDAT
830 * chunks which are longer than zero as well:
832 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
833 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
834 png_benign_error(png_ptr, "..Too many IDATs found");
836 png_crc_finish(png_ptr, length);
838 else if (chunk_name == png_PLTE)
839 png_handle_PLTE(png_ptr, info_ptr, length);
841 #ifdef PNG_READ_bKGD_SUPPORTED
842 else if (chunk_name == png_bKGD)
843 png_handle_bKGD(png_ptr, info_ptr, length);
844 #endif
846 #ifdef PNG_READ_cHRM_SUPPORTED
847 else if (chunk_name == png_cHRM)
848 png_handle_cHRM(png_ptr, info_ptr, length);
849 #endif
851 #ifdef PNG_READ_eXIf_SUPPORTED
852 else if (chunk_name == png_eXIf)
853 png_handle_eXIf(png_ptr, info_ptr, length);
854 #endif
856 #ifdef PNG_READ_gAMA_SUPPORTED
857 else if (chunk_name == png_gAMA)
858 png_handle_gAMA(png_ptr, info_ptr, length);
859 #endif
861 #ifdef PNG_READ_hIST_SUPPORTED
862 else if (chunk_name == png_hIST)
863 png_handle_hIST(png_ptr, info_ptr, length);
864 #endif
866 #ifdef PNG_READ_oFFs_SUPPORTED
867 else if (chunk_name == png_oFFs)
868 png_handle_oFFs(png_ptr, info_ptr, length);
869 #endif
871 #ifdef PNG_READ_pCAL_SUPPORTED
872 else if (chunk_name == png_pCAL)
873 png_handle_pCAL(png_ptr, info_ptr, length);
874 #endif
876 #ifdef PNG_READ_sCAL_SUPPORTED
877 else if (chunk_name == png_sCAL)
878 png_handle_sCAL(png_ptr, info_ptr, length);
879 #endif
881 #ifdef PNG_READ_pHYs_SUPPORTED
882 else if (chunk_name == png_pHYs)
883 png_handle_pHYs(png_ptr, info_ptr, length);
884 #endif
886 #ifdef PNG_READ_sBIT_SUPPORTED
887 else if (chunk_name == png_sBIT)
888 png_handle_sBIT(png_ptr, info_ptr, length);
889 #endif
891 #ifdef PNG_READ_sRGB_SUPPORTED
892 else if (chunk_name == png_sRGB)
893 png_handle_sRGB(png_ptr, info_ptr, length);
894 #endif
896 #ifdef PNG_READ_iCCP_SUPPORTED
897 else if (chunk_name == png_iCCP)
898 png_handle_iCCP(png_ptr, info_ptr, length);
899 #endif
901 #ifdef PNG_READ_sPLT_SUPPORTED
902 else if (chunk_name == png_sPLT)
903 png_handle_sPLT(png_ptr, info_ptr, length);
904 #endif
906 #ifdef PNG_READ_tEXt_SUPPORTED
907 else if (chunk_name == png_tEXt)
908 png_handle_tEXt(png_ptr, info_ptr, length);
909 #endif
911 #ifdef PNG_READ_tIME_SUPPORTED
912 else if (chunk_name == png_tIME)
913 png_handle_tIME(png_ptr, info_ptr, length);
914 #endif
916 #ifdef PNG_READ_tRNS_SUPPORTED
917 else if (chunk_name == png_tRNS)
918 png_handle_tRNS(png_ptr, info_ptr, length);
919 #endif
921 #ifdef PNG_READ_zTXt_SUPPORTED
922 else if (chunk_name == png_zTXt)
923 png_handle_zTXt(png_ptr, info_ptr, length);
924 #endif
926 #ifdef PNG_READ_iTXt_SUPPORTED
927 else if (chunk_name == png_iTXt)
928 png_handle_iTXt(png_ptr, info_ptr, length);
929 #endif
931 else
932 png_handle_unknown(png_ptr, info_ptr, length,
933 PNG_HANDLE_CHUNK_AS_DEFAULT);
934 } while ((png_ptr->mode & PNG_HAVE_IEND) == 0);
936 #endif /* SEQUENTIAL_READ */
938 /* Free all memory used in the read struct */
939 static void
940 png_read_destroy(png_structrp png_ptr)
942 png_debug(1, "in png_read_destroy");
944 #ifdef PNG_READ_GAMMA_SUPPORTED
945 png_destroy_gamma_table(png_ptr);
946 #endif
948 png_free(png_ptr, png_ptr->big_row_buf);
949 png_ptr->big_row_buf = NULL;
950 png_free(png_ptr, png_ptr->big_prev_row);
951 png_ptr->big_prev_row = NULL;
952 png_free(png_ptr, png_ptr->read_buffer);
953 png_ptr->read_buffer = NULL;
955 #ifdef PNG_READ_QUANTIZE_SUPPORTED
956 png_free(png_ptr, png_ptr->palette_lookup);
957 png_ptr->palette_lookup = NULL;
958 png_free(png_ptr, png_ptr->quantize_index);
959 png_ptr->quantize_index = NULL;
960 #endif
962 if ((png_ptr->free_me & PNG_FREE_PLTE) != 0)
964 png_zfree(png_ptr, png_ptr->palette);
965 png_ptr->palette = NULL;
967 png_ptr->free_me &= ~PNG_FREE_PLTE;
969 #if defined(PNG_tRNS_SUPPORTED) || \
970 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
971 if ((png_ptr->free_me & PNG_FREE_TRNS) != 0)
973 png_free(png_ptr, png_ptr->trans_alpha);
974 png_ptr->trans_alpha = NULL;
976 png_ptr->free_me &= ~PNG_FREE_TRNS;
977 #endif
979 inflateEnd(&png_ptr->zstream);
981 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
982 png_free(png_ptr, png_ptr->save_buffer);
983 png_ptr->save_buffer = NULL;
984 #endif
986 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) && \
987 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
988 png_free(png_ptr, png_ptr->unknown_chunk.data);
989 png_ptr->unknown_chunk.data = NULL;
990 #endif
992 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
993 png_free(png_ptr, png_ptr->chunk_list);
994 png_ptr->chunk_list = NULL;
995 #endif
997 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
998 * callbacks are still set at this point. They are required to complete the
999 * destruction of the png_struct itself.
1003 /* Free all memory used by the read */
1004 void PNGAPI
1005 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
1006 png_infopp end_info_ptr_ptr)
1008 png_structrp png_ptr = NULL;
1010 png_debug(1, "in png_destroy_read_struct");
1012 if (png_ptr_ptr != NULL)
1013 png_ptr = *png_ptr_ptr;
1015 if (png_ptr == NULL)
1016 return;
1018 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1019 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1020 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1022 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
1023 png_destroy_info_struct(png_ptr, info_ptr_ptr);
1025 *png_ptr_ptr = NULL;
1026 png_read_destroy(png_ptr);
1027 png_destroy_png_struct(png_ptr);
1030 void PNGAPI
1031 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
1033 if (png_ptr == NULL)
1034 return;
1036 png_ptr->read_row_fn = read_row_fn;
1040 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1041 #ifdef PNG_INFO_IMAGE_SUPPORTED
1042 void PNGAPI
1043 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1044 int transforms, voidp params)
1046 if (png_ptr == NULL || info_ptr == NULL)
1047 return;
1049 /* png_read_info() gives us all of the information from the
1050 * PNG file before the first IDAT (image data chunk).
1052 png_read_info(png_ptr, info_ptr);
1053 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1054 png_error(png_ptr, "Image is too high to process with png_read_png()");
1056 /* -------------- image transformations start here ------------------- */
1057 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1058 * is not implemented. This will only happen in de-configured (non-default)
1059 * libpng builds. The results can be unexpected - png_read_png may return
1060 * short or mal-formed rows because the transform is skipped.
1063 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1065 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
1066 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1067 * did in earlier versions, while "scale_16" is now more accurate.
1069 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1070 png_set_scale_16(png_ptr);
1071 #else
1072 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1073 #endif
1075 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1076 * latter by doing SCALE first. This is ok and allows apps not to check for
1077 * which is supported to get the right answer.
1079 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
1080 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1081 png_set_strip_16(png_ptr);
1082 #else
1083 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1084 #endif
1086 /* Strip alpha bytes from the input data without combining with
1087 * the background (not recommended).
1089 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
1090 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1091 png_set_strip_alpha(png_ptr);
1092 #else
1093 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1094 #endif
1096 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1097 * byte into separate bytes (useful for paletted and grayscale images).
1099 if ((transforms & PNG_TRANSFORM_PACKING) != 0)
1100 #ifdef PNG_READ_PACK_SUPPORTED
1101 png_set_packing(png_ptr);
1102 #else
1103 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1104 #endif
1106 /* Change the order of packed pixels to least significant bit first
1107 * (not useful if you are using png_set_packing).
1109 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
1110 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1111 png_set_packswap(png_ptr);
1112 #else
1113 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1114 #endif
1116 /* Expand paletted colors into true RGB triplets
1117 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1118 * Expand paletted or RGB images with transparency to full alpha
1119 * channels so the data will be available as RGBA quartets.
1121 if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
1122 #ifdef PNG_READ_EXPAND_SUPPORTED
1123 png_set_expand(png_ptr);
1124 #else
1125 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1126 #endif
1128 /* We don't handle background color or gamma transformation or quantizing.
1131 /* Invert monochrome files to have 0 as white and 1 as black
1133 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
1134 #ifdef PNG_READ_INVERT_SUPPORTED
1135 png_set_invert_mono(png_ptr);
1136 #else
1137 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1138 #endif
1140 /* If you want to shift the pixel values from the range [0,255] or
1141 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1142 * colors were originally in:
1144 if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
1145 #ifdef PNG_READ_SHIFT_SUPPORTED
1146 if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
1147 png_set_shift(png_ptr, &info_ptr->sig_bit);
1148 #else
1149 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1150 #endif
1152 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1153 if ((transforms & PNG_TRANSFORM_BGR) != 0)
1154 #ifdef PNG_READ_BGR_SUPPORTED
1155 png_set_bgr(png_ptr);
1156 #else
1157 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1158 #endif
1160 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1161 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
1162 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1163 png_set_swap_alpha(png_ptr);
1164 #else
1165 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1166 #endif
1168 /* Swap bytes of 16-bit files to least significant byte first */
1169 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
1170 #ifdef PNG_READ_SWAP_SUPPORTED
1171 png_set_swap(png_ptr);
1172 #else
1173 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1174 #endif
1176 /* Added at libpng-1.2.41 */
1177 /* Invert the alpha channel from opacity to transparency */
1178 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
1179 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1180 png_set_invert_alpha(png_ptr);
1181 #else
1182 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1183 #endif
1185 /* Added at libpng-1.2.41 */
1186 /* Expand grayscale image to RGB */
1187 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
1188 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1189 png_set_gray_to_rgb(png_ptr);
1190 #else
1191 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1192 #endif
1194 /* Added at libpng-1.5.4 */
1195 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
1196 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1197 png_set_expand_16(png_ptr);
1198 #else
1199 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1200 #endif
1202 /* We don't handle adding filler bytes */
1204 /* We use png_read_image and rely on that for interlace handling, but we also
1205 * call png_read_update_info therefore must turn on interlace handling now:
1207 (void)png_set_interlace_handling(png_ptr);
1209 /* Optional call to gamma correct and add the background to the palette
1210 * and update info structure. REQUIRED if you are expecting libpng to
1211 * update the palette for you (i.e., you selected such a transform above).
1213 png_read_update_info(png_ptr, info_ptr);
1215 /* -------------- image transformations end here ------------------- */
1217 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1218 if (info_ptr->row_pointers == NULL)
1220 png_uint_32 iptr;
1222 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1223 info_ptr->height * (sizeof (png_bytep))));
1225 for (iptr=0; iptr<info_ptr->height; iptr++)
1226 info_ptr->row_pointers[iptr] = NULL;
1228 info_ptr->free_me |= PNG_FREE_ROWS;
1230 for (iptr = 0; iptr < info_ptr->height; iptr++)
1231 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1232 png_malloc(png_ptr, info_ptr->rowbytes));
1235 png_read_image(png_ptr, info_ptr->row_pointers);
1236 info_ptr->valid |= PNG_INFO_IDAT;
1238 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1239 png_read_end(png_ptr, info_ptr);
1241 PNG_UNUSED(params)
1243 #endif /* INFO_IMAGE */
1244 #endif /* SEQUENTIAL_READ */
1246 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1247 /* SIMPLIFIED READ
1249 * This code currently relies on the sequential reader, though it could easily
1250 * be made to work with the progressive one.
1252 /* Arguments to png_image_finish_read: */
1254 /* Encoding of PNG data (used by the color-map code) */
1255 # define P_NOTSET 0 /* File encoding not yet known */
1256 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1257 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1258 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1259 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1261 /* Color-map processing: after libpng has run on the PNG image further
1262 * processing may be needed to convert the data to color-map indices.
1264 #define PNG_CMAP_NONE 0
1265 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1266 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1267 #define PNG_CMAP_RGB 3 /* Process RGB data */
1268 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1270 /* The following document where the background is for each processing case. */
1271 #define PNG_CMAP_NONE_BACKGROUND 256
1272 #define PNG_CMAP_GA_BACKGROUND 231
1273 #define PNG_CMAP_TRANS_BACKGROUND 254
1274 #define PNG_CMAP_RGB_BACKGROUND 256
1275 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1277 typedef struct
1279 /* Arguments: */
1280 png_imagep image;
1281 png_voidp buffer;
1282 png_int_32 row_stride;
1283 png_voidp colormap;
1284 png_const_colorp background;
1285 /* Local variables: */
1286 png_voidp local_row;
1287 png_voidp first_row;
1288 ptrdiff_t row_bytes; /* step between rows */
1289 int file_encoding; /* E_ values above */
1290 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1291 int colormap_processing; /* PNG_CMAP_ values above */
1292 } png_image_read_control;
1294 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1295 * called, so setting up the jmp_buf is not required. This means that anything
1296 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1297 * instead so that control is returned safely back to this routine.
1299 static int
1300 png_image_read_init(png_imagep image)
1302 if (image->opaque == NULL)
1304 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1305 png_safe_error, png_safe_warning);
1307 /* And set the rest of the structure to NULL to ensure that the various
1308 * fields are consistent.
1310 memset(image, 0, (sizeof *image));
1311 image->version = PNG_IMAGE_VERSION;
1313 if (png_ptr != NULL)
1315 png_infop info_ptr = png_create_info_struct(png_ptr);
1317 if (info_ptr != NULL)
1319 png_controlp control = png_voidcast(png_controlp,
1320 png_malloc_warn(png_ptr, (sizeof *control)));
1322 if (control != NULL)
1324 memset(control, 0, (sizeof *control));
1326 control->png_ptr = png_ptr;
1327 control->info_ptr = info_ptr;
1328 control->for_write = 0;
1330 image->opaque = control;
1331 return 1;
1334 /* Error clean up */
1335 png_destroy_info_struct(png_ptr, &info_ptr);
1338 png_destroy_read_struct(&png_ptr, NULL, NULL);
1341 return png_image_error(image, "png_image_read: out of memory");
1344 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1347 /* Utility to find the base format of a PNG file from a png_struct. */
1348 static png_uint_32
1349 png_image_format(png_structrp png_ptr)
1351 png_uint_32 format = 0;
1353 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1354 format |= PNG_FORMAT_FLAG_COLOR;
1356 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
1357 format |= PNG_FORMAT_FLAG_ALPHA;
1359 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1360 * sets the png_struct fields; that's all we are interested in here. The
1361 * precise interaction with an app call to png_set_tRNS and PNG file reading
1362 * is unclear.
1364 else if (png_ptr->num_trans > 0)
1365 format |= PNG_FORMAT_FLAG_ALPHA;
1367 if (png_ptr->bit_depth == 16)
1368 format |= PNG_FORMAT_FLAG_LINEAR;
1370 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
1371 format |= PNG_FORMAT_FLAG_COLORMAP;
1373 return format;
1376 /* Is the given gamma significantly different from sRGB? The test is the same
1377 * one used in pngrtran.c when deciding whether to do gamma correction. The
1378 * arithmetic optimizes the division by using the fact that the inverse of the
1379 * file sRGB gamma is 2.2
1381 static int
1382 png_gamma_not_sRGB(png_fixed_point g)
1384 if (g < PNG_FP_1)
1386 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1387 if (g == 0)
1388 return 0;
1390 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1393 return 1;
1396 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1397 * header and fill in all the information. This is executed in a safe context,
1398 * unlike the init routine above.
1400 static int
1401 png_image_read_header(png_voidp argument)
1403 png_imagep image = png_voidcast(png_imagep, argument);
1404 png_structrp png_ptr = image->opaque->png_ptr;
1405 png_inforp info_ptr = image->opaque->info_ptr;
1407 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
1408 png_set_benign_errors(png_ptr, 1/*warn*/);
1409 #endif
1410 png_read_info(png_ptr, info_ptr);
1412 /* Do this the fast way; just read directly out of png_struct. */
1413 image->width = png_ptr->width;
1414 image->height = png_ptr->height;
1417 png_uint_32 format = png_image_format(png_ptr);
1419 image->format = format;
1421 #ifdef PNG_COLORSPACE_SUPPORTED
1422 /* Does the colorspace match sRGB? If there is no color endpoint
1423 * (colorant) information assume yes, otherwise require the
1424 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1425 * colorspace has been determined to be invalid ignore it.
1427 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1428 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1429 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1430 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1431 #endif
1434 /* We need the maximum number of entries regardless of the format the
1435 * application sets here.
1438 png_uint_32 cmap_entries;
1440 switch (png_ptr->color_type)
1442 case PNG_COLOR_TYPE_GRAY:
1443 cmap_entries = 1U << png_ptr->bit_depth;
1444 break;
1446 case PNG_COLOR_TYPE_PALETTE:
1447 cmap_entries = (png_uint_32)png_ptr->num_palette;
1448 break;
1450 default:
1451 cmap_entries = 256;
1452 break;
1455 if (cmap_entries > 256)
1456 cmap_entries = 256;
1458 image->colormap_entries = cmap_entries;
1461 return 1;
1464 #ifdef PNG_STDIO_SUPPORTED
1465 int PNGAPI
1466 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1468 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1470 if (file != NULL)
1472 if (png_image_read_init(image) != 0)
1474 /* This is slightly evil, but png_init_io doesn't do anything other
1475 * than this and we haven't changed the standard IO functions so
1476 * this saves a 'safe' function.
1478 image->opaque->png_ptr->io_ptr = file;
1479 return png_safe_execute(image, png_image_read_header, image);
1483 else
1484 return png_image_error(image,
1485 "png_image_begin_read_from_stdio: invalid argument");
1488 else if (image != NULL)
1489 return png_image_error(image,
1490 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1492 return 0;
1495 int PNGAPI
1496 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1498 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1500 if (file_name != NULL)
1502 FILE *fp = fopen(file_name, "rb");
1504 if (fp != NULL)
1506 if (png_image_read_init(image) != 0)
1508 image->opaque->png_ptr->io_ptr = fp;
1509 image->opaque->owned_file = 1;
1510 return png_safe_execute(image, png_image_read_header, image);
1513 /* Clean up: just the opened file. */
1514 (void)fclose(fp);
1517 else
1518 return png_image_error(image, strerror(errno));
1521 else
1522 return png_image_error(image,
1523 "png_image_begin_read_from_file: invalid argument");
1526 else if (image != NULL)
1527 return png_image_error(image,
1528 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1530 return 0;
1532 #endif /* STDIO */
1534 static void PNGCBAPI
1535 png_image_memory_read(png_structp png_ptr, png_bytep out, size_t need)
1537 if (png_ptr != NULL)
1539 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1540 if (image != NULL)
1542 png_controlp cp = image->opaque;
1543 if (cp != NULL)
1545 png_const_bytep memory = cp->memory;
1546 size_t size = cp->size;
1548 if (memory != NULL && size >= need)
1550 memcpy(out, memory, need);
1551 cp->memory = memory + need;
1552 cp->size = size - need;
1553 return;
1556 png_error(png_ptr, "read beyond end of data");
1560 png_error(png_ptr, "invalid memory read");
1564 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1565 png_const_voidp memory, size_t size)
1567 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1569 if (memory != NULL && size > 0)
1571 if (png_image_read_init(image) != 0)
1573 /* Now set the IO functions to read from the memory buffer and
1574 * store it into io_ptr. Again do this in-place to avoid calling a
1575 * libpng function that requires error handling.
1577 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1578 image->opaque->size = size;
1579 image->opaque->png_ptr->io_ptr = image;
1580 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1582 return png_safe_execute(image, png_image_read_header, image);
1586 else
1587 return png_image_error(image,
1588 "png_image_begin_read_from_memory: invalid argument");
1591 else if (image != NULL)
1592 return png_image_error(image,
1593 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1595 return 0;
1598 /* Utility function to skip chunks that are not used by the simplified image
1599 * read functions and an appropriate macro to call it.
1601 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1602 static void
1603 png_image_skip_unused_chunks(png_structrp png_ptr)
1605 /* Prepare the reader to ignore all recognized chunks whose data will not
1606 * be used, i.e., all chunks recognized by libpng except for those
1607 * involved in basic image reading:
1609 * IHDR, PLTE, IDAT, IEND
1611 * Or image data handling:
1613 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1615 * This provides a small performance improvement and eliminates any
1616 * potential vulnerability to security problems in the unused chunks.
1618 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1619 * too. This allows the simplified API to be compiled without iCCP support,
1620 * however if the support is there the chunk is still checked to detect
1621 * errors (which are unfortunately quite common.)
1624 static const png_byte chunks_to_process[] = {
1625 98, 75, 71, 68, '\0', /* bKGD */
1626 99, 72, 82, 77, '\0', /* cHRM */
1627 103, 65, 77, 65, '\0', /* gAMA */
1628 # ifdef PNG_READ_iCCP_SUPPORTED
1629 105, 67, 67, 80, '\0', /* iCCP */
1630 # endif
1631 115, 66, 73, 84, '\0', /* sBIT */
1632 115, 82, 71, 66, '\0', /* sRGB */
1635 /* Ignore unknown chunks and all other chunks except for the
1636 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1638 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1639 NULL, -1);
1641 /* But do not ignore image data handling chunks */
1642 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1643 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
1647 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1648 #else
1649 # define PNG_SKIP_CHUNKS(p) ((void)0)
1650 #endif /* HANDLE_AS_UNKNOWN */
1652 /* The following macro gives the exact rounded answer for all values in the
1653 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1654 * the correct numbers 0..5
1656 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1658 /* Utility functions to make particular color-maps */
1659 static void
1660 set_file_encoding(png_image_read_control *display)
1662 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1663 if (png_gamma_significant(g) != 0)
1665 if (png_gamma_not_sRGB(g) != 0)
1667 display->file_encoding = P_FILE;
1668 display->gamma_to_linear = png_reciprocal(g);
1671 else
1672 display->file_encoding = P_sRGB;
1675 else
1676 display->file_encoding = P_LINEAR8;
1679 static unsigned int
1680 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1682 if (encoding == P_FILE) /* double check */
1683 encoding = display->file_encoding;
1685 if (encoding == P_NOTSET) /* must be the file encoding */
1687 set_file_encoding(display);
1688 encoding = display->file_encoding;
1691 switch (encoding)
1693 case P_FILE:
1694 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1695 break;
1697 case P_sRGB:
1698 value = png_sRGB_table[value];
1699 break;
1701 case P_LINEAR:
1702 break;
1704 case P_LINEAR8:
1705 value *= 257;
1706 break;
1708 #ifdef __GNUC__
1709 default:
1710 png_error(display->image->opaque->png_ptr,
1711 "unexpected encoding (internal error)");
1712 #endif
1715 return value;
1718 static png_uint_32
1719 png_colormap_compose(png_image_read_control *display,
1720 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1721 png_uint_32 background, int encoding)
1723 /* The file value is composed on the background, the background has the given
1724 * encoding and so does the result, the file is encoded with P_FILE and the
1725 * file and alpha are 8-bit values. The (output) encoding will always be
1726 * P_LINEAR or P_sRGB.
1728 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1729 png_uint_32 b = decode_gamma(display, background, encoding);
1731 /* The alpha is always an 8-bit value (it comes from the palette), the value
1732 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1734 f = f * alpha + b * (255-alpha);
1736 if (encoding == P_LINEAR)
1738 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1739 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1741 f *= 257; /* Now scaled by 65535 */
1742 f += f >> 16;
1743 f = (f+32768) >> 16;
1746 else /* P_sRGB */
1747 f = PNG_sRGB_FROM_LINEAR(f);
1749 return f;
1752 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1753 * be 8-bit.
1755 static void
1756 png_create_colormap_entry(png_image_read_control *display,
1757 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1758 png_uint_32 alpha, int encoding)
1760 png_imagep image = display->image;
1761 int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
1762 P_LINEAR : P_sRGB;
1763 int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1764 (red != green || green != blue);
1766 if (ip > 255)
1767 png_error(image->opaque->png_ptr, "color-map index out of range");
1769 /* Update the cache with whether the file gamma is significantly different
1770 * from sRGB.
1772 if (encoding == P_FILE)
1774 if (display->file_encoding == P_NOTSET)
1775 set_file_encoding(display);
1777 /* Note that the cached value may be P_FILE too, but if it is then the
1778 * gamma_to_linear member has been set.
1780 encoding = display->file_encoding;
1783 if (encoding == P_FILE)
1785 png_fixed_point g = display->gamma_to_linear;
1787 red = png_gamma_16bit_correct(red*257, g);
1788 green = png_gamma_16bit_correct(green*257, g);
1789 blue = png_gamma_16bit_correct(blue*257, g);
1791 if (convert_to_Y != 0 || output_encoding == P_LINEAR)
1793 alpha *= 257;
1794 encoding = P_LINEAR;
1797 else
1799 red = PNG_sRGB_FROM_LINEAR(red * 255);
1800 green = PNG_sRGB_FROM_LINEAR(green * 255);
1801 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1802 encoding = P_sRGB;
1806 else if (encoding == P_LINEAR8)
1808 /* This encoding occurs quite frequently in test cases because PngSuite
1809 * includes a gAMA 1.0 chunk with most images.
1811 red *= 257;
1812 green *= 257;
1813 blue *= 257;
1814 alpha *= 257;
1815 encoding = P_LINEAR;
1818 else if (encoding == P_sRGB &&
1819 (convert_to_Y != 0 || output_encoding == P_LINEAR))
1821 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1822 * linear.
1824 red = png_sRGB_table[red];
1825 green = png_sRGB_table[green];
1826 blue = png_sRGB_table[blue];
1827 alpha *= 257;
1828 encoding = P_LINEAR;
1831 /* This is set if the color isn't gray but the output is. */
1832 if (encoding == P_LINEAR)
1834 if (convert_to_Y != 0)
1836 /* NOTE: these values are copied from png_do_rgb_to_gray */
1837 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1838 (png_uint_32)2366 * blue;
1840 if (output_encoding == P_LINEAR)
1841 y = (y + 16384) >> 15;
1843 else
1845 /* y is scaled by 32768, we need it scaled by 255: */
1846 y = (y + 128) >> 8;
1847 y *= 255;
1848 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1849 alpha = PNG_DIV257(alpha);
1850 encoding = P_sRGB;
1853 blue = red = green = y;
1856 else if (output_encoding == P_sRGB)
1858 red = PNG_sRGB_FROM_LINEAR(red * 255);
1859 green = PNG_sRGB_FROM_LINEAR(green * 255);
1860 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1861 alpha = PNG_DIV257(alpha);
1862 encoding = P_sRGB;
1866 if (encoding != output_encoding)
1867 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1869 /* Store the value. */
1871 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1872 int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1873 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1874 # else
1875 # define afirst 0
1876 # endif
1877 # ifdef PNG_FORMAT_BGR_SUPPORTED
1878 int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
1879 # else
1880 # define bgr 0
1881 # endif
1883 if (output_encoding == P_LINEAR)
1885 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1887 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1889 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1890 * value, if less than 65535 (this is, effectively, composite on black
1891 * if the alpha channel is removed.)
1893 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1895 case 4:
1896 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
1897 /* FALLTHROUGH */
1899 case 3:
1900 if (alpha < 65535)
1902 if (alpha > 0)
1904 blue = (blue * alpha + 32767U)/65535U;
1905 green = (green * alpha + 32767U)/65535U;
1906 red = (red * alpha + 32767U)/65535U;
1909 else
1910 red = green = blue = 0;
1912 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
1913 entry[afirst + 1] = (png_uint_16)green;
1914 entry[afirst + bgr] = (png_uint_16)red;
1915 break;
1917 case 2:
1918 entry[1 ^ afirst] = (png_uint_16)alpha;
1919 /* FALLTHROUGH */
1921 case 1:
1922 if (alpha < 65535)
1924 if (alpha > 0)
1925 green = (green * alpha + 32767U)/65535U;
1927 else
1928 green = 0;
1930 entry[afirst] = (png_uint_16)green;
1931 break;
1933 default:
1934 break;
1938 else /* output encoding is P_sRGB */
1940 png_bytep entry = png_voidcast(png_bytep, display->colormap);
1942 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1944 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1946 case 4:
1947 entry[afirst ? 0 : 3] = (png_byte)alpha;
1948 /* FALLTHROUGH */
1949 case 3:
1950 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
1951 entry[afirst + 1] = (png_byte)green;
1952 entry[afirst + bgr] = (png_byte)red;
1953 break;
1955 case 2:
1956 entry[1 ^ afirst] = (png_byte)alpha;
1957 /* FALLTHROUGH */
1958 case 1:
1959 entry[afirst] = (png_byte)green;
1960 break;
1962 default:
1963 break;
1967 # ifdef afirst
1968 # undef afirst
1969 # endif
1970 # ifdef bgr
1971 # undef bgr
1972 # endif
1976 static int
1977 make_gray_file_colormap(png_image_read_control *display)
1979 unsigned int i;
1981 for (i=0; i<256; ++i)
1982 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
1984 return (int)i;
1987 static int
1988 make_gray_colormap(png_image_read_control *display)
1990 unsigned int i;
1992 for (i=0; i<256; ++i)
1993 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
1995 return (int)i;
1997 #define PNG_GRAY_COLORMAP_ENTRIES 256
1999 static int
2000 make_ga_colormap(png_image_read_control *display)
2002 unsigned int i, a;
2004 /* Alpha is retained, the output will be a color-map with entries
2005 * selected by six levels of alpha. One transparent entry, 6 gray
2006 * levels for all the intermediate alpha values, leaving 230 entries
2007 * for the opaque grays. The color-map entries are the six values
2008 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
2009 * relevant entry.
2011 * if (alpha > 229) // opaque
2013 * // The 231 entries are selected to make the math below work:
2014 * base = 0;
2015 * entry = (231 * gray + 128) >> 8;
2017 * else if (alpha < 26) // transparent
2019 * base = 231;
2020 * entry = 0;
2022 * else // partially opaque
2024 * base = 226 + 6 * PNG_DIV51(alpha);
2025 * entry = PNG_DIV51(gray);
2028 i = 0;
2029 while (i < 231)
2031 unsigned int gray = (i * 256 + 115) / 231;
2032 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2035 /* 255 is used here for the component values for consistency with the code
2036 * that undoes premultiplication in pngwrite.c.
2038 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2040 for (a=1; a<5; ++a)
2042 unsigned int g;
2044 for (g=0; g<6; ++g)
2045 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2046 P_sRGB);
2049 return (int)i;
2052 #define PNG_GA_COLORMAP_ENTRIES 256
2054 static int
2055 make_rgb_colormap(png_image_read_control *display)
2057 unsigned int i, r;
2059 /* Build a 6x6x6 opaque RGB cube */
2060 for (i=r=0; r<6; ++r)
2062 unsigned int g;
2064 for (g=0; g<6; ++g)
2066 unsigned int b;
2068 for (b=0; b<6; ++b)
2069 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2070 P_sRGB);
2074 return (int)i;
2077 #define PNG_RGB_COLORMAP_ENTRIES 216
2079 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2080 #define PNG_RGB_INDEX(r,g,b) \
2081 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2083 static int
2084 png_image_read_colormap(png_voidp argument)
2086 png_image_read_control *display =
2087 png_voidcast(png_image_read_control*, argument);
2088 png_imagep image = display->image;
2090 png_structrp png_ptr = image->opaque->png_ptr;
2091 png_uint_32 output_format = image->format;
2092 int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
2093 P_LINEAR : P_sRGB;
2095 unsigned int cmap_entries;
2096 unsigned int output_processing; /* Output processing option */
2097 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2099 /* Background information; the background color and the index of this color
2100 * in the color-map if it exists (else 256).
2102 unsigned int background_index = 256;
2103 png_uint_32 back_r, back_g, back_b;
2105 /* Flags to accumulate things that need to be done to the input. */
2106 int expand_tRNS = 0;
2108 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2109 * very difficult to do, the results look awful, and it is difficult to see
2110 * what possible use it is because the application can't control the
2111 * color-map.
2113 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2114 png_ptr->num_trans > 0) /* alpha in input */ &&
2115 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2117 if (output_encoding == P_LINEAR) /* compose on black */
2118 back_b = back_g = back_r = 0;
2120 else if (display->background == NULL /* no way to remove it */)
2121 png_error(png_ptr,
2122 "background color must be supplied to remove alpha/transparency");
2124 /* Get a copy of the background color (this avoids repeating the checks
2125 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2126 * output format.
2128 else
2130 back_g = display->background->green;
2131 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
2133 back_r = display->background->red;
2134 back_b = display->background->blue;
2136 else
2137 back_b = back_r = back_g;
2141 else if (output_encoding == P_LINEAR)
2142 back_b = back_r = back_g = 65535;
2144 else
2145 back_b = back_r = back_g = 255;
2147 /* Default the input file gamma if required - this is necessary because
2148 * libpng assumes that if no gamma information is present the data is in the
2149 * output format, but the simplified API deduces the gamma from the input
2150 * format.
2152 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2154 /* Do this directly, not using the png_colorspace functions, to ensure
2155 * that it happens even if the colorspace is invalid (though probably if
2156 * it is the setting will be ignored) Note that the same thing can be
2157 * achieved at the application interface with png_set_gAMA.
2159 if (png_ptr->bit_depth == 16 &&
2160 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2161 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2163 else
2164 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2166 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2169 /* Decide what to do based on the PNG color type of the input data. The
2170 * utility function png_create_colormap_entry deals with most aspects of the
2171 * output transformations; this code works out how to produce bytes of
2172 * color-map entries from the original format.
2174 switch (png_ptr->color_type)
2176 case PNG_COLOR_TYPE_GRAY:
2177 if (png_ptr->bit_depth <= 8)
2179 /* There at most 256 colors in the output, regardless of
2180 * transparency.
2182 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2184 cmap_entries = 1U << png_ptr->bit_depth;
2185 if (cmap_entries > image->colormap_entries)
2186 png_error(png_ptr, "gray[8] color-map: too few entries");
2188 step = 255 / (cmap_entries - 1);
2189 output_processing = PNG_CMAP_NONE;
2191 /* If there is a tRNS chunk then this either selects a transparent
2192 * value or, if the output has no alpha, the background color.
2194 if (png_ptr->num_trans > 0)
2196 trans = png_ptr->trans_color.gray;
2198 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2199 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2202 /* png_create_colormap_entry just takes an RGBA and writes the
2203 * corresponding color-map entry using the format from 'image',
2204 * including the required conversion to sRGB or linear as
2205 * appropriate. The input values are always either sRGB (if the
2206 * gamma correction flag is 0) or 0..255 scaled file encoded values
2207 * (if the function must gamma correct them).
2209 for (i=val=0; i<cmap_entries; ++i, val += step)
2211 /* 'i' is a file value. While this will result in duplicated
2212 * entries for 8-bit non-sRGB encoded files it is necessary to
2213 * have non-gamma corrected values to do tRNS handling.
2215 if (i != trans)
2216 png_create_colormap_entry(display, i, val, val, val, 255,
2217 P_FILE/*8-bit with file gamma*/);
2219 /* Else this entry is transparent. The colors don't matter if
2220 * there is an alpha channel (back_alpha == 0), but it does no
2221 * harm to pass them in; the values are not set above so this
2222 * passes in white.
2224 * NOTE: this preserves the full precision of the application
2225 * supplied background color when it is used.
2227 else
2228 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2229 back_alpha, output_encoding);
2232 /* We need libpng to preserve the original encoding. */
2233 data_encoding = P_FILE;
2235 /* The rows from libpng, while technically gray values, are now also
2236 * color-map indices; however, they may need to be expanded to 1
2237 * byte per pixel. This is what png_set_packing does (i.e., it
2238 * unpacks the bit values into bytes.)
2240 if (png_ptr->bit_depth < 8)
2241 png_set_packing(png_ptr);
2244 else /* bit depth is 16 */
2246 /* The 16-bit input values can be converted directly to 8-bit gamma
2247 * encoded values; however, if a tRNS chunk is present 257 color-map
2248 * entries are required. This means that the extra entry requires
2249 * special processing; add an alpha channel, sacrifice gray level
2250 * 254 and convert transparent (alpha==0) entries to that.
2252 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2253 * same time to minimize quality loss. If a tRNS chunk is present
2254 * this means libpng must handle it too; otherwise it is impossible
2255 * to do the exact match on the 16-bit value.
2257 * If the output has no alpha channel *and* the background color is
2258 * gray then it is possible to let libpng handle the substitution by
2259 * ensuring that the corresponding gray level matches the background
2260 * color exactly.
2262 data_encoding = P_sRGB;
2264 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2265 png_error(png_ptr, "gray[16] color-map: too few entries");
2267 cmap_entries = (unsigned int)make_gray_colormap(display);
2269 if (png_ptr->num_trans > 0)
2271 unsigned int back_alpha;
2273 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2274 back_alpha = 0;
2276 else
2278 if (back_r == back_g && back_g == back_b)
2280 /* Background is gray; no special processing will be
2281 * required.
2283 png_color_16 c;
2284 png_uint_32 gray = back_g;
2286 if (output_encoding == P_LINEAR)
2288 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2290 /* And make sure the corresponding palette entry
2291 * matches.
2293 png_create_colormap_entry(display, gray, back_g, back_g,
2294 back_g, 65535, P_LINEAR);
2297 /* The background passed to libpng, however, must be the
2298 * sRGB value.
2300 c.index = 0; /*unused*/
2301 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2303 /* NOTE: does this work without expanding tRNS to alpha?
2304 * It should be the color->gray case below apparently
2305 * doesn't.
2307 png_set_background_fixed(png_ptr, &c,
2308 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2309 0/*gamma: not used*/);
2311 output_processing = PNG_CMAP_NONE;
2312 break;
2314 #ifdef __COVERITY__
2315 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2316 * here.
2318 back_alpha = 255;
2319 #else
2320 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2321 #endif
2324 /* output_processing means that the libpng-processed row will be
2325 * 8-bit GA and it has to be processing to single byte color-map
2326 * values. Entry 254 is replaced by either a completely
2327 * transparent entry or by the background color at full
2328 * precision (and the background color is not a simple gray
2329 * level in this case.)
2331 expand_tRNS = 1;
2332 output_processing = PNG_CMAP_TRANS;
2333 background_index = 254;
2335 /* And set (overwrite) color-map entry 254 to the actual
2336 * background color at full precision.
2338 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2339 back_alpha, output_encoding);
2342 else
2343 output_processing = PNG_CMAP_NONE;
2345 break;
2347 case PNG_COLOR_TYPE_GRAY_ALPHA:
2348 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2349 * of 65536 combinations. If, however, the alpha channel is to be
2350 * removed there are only 256 possibilities if the background is gray.
2351 * (Otherwise there is a subset of the 65536 possibilities defined by
2352 * the triangle between black, white and the background color.)
2354 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2355 * worry about tRNS matching - tRNS is ignored if there is an alpha
2356 * channel.
2358 data_encoding = P_sRGB;
2360 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2362 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2363 png_error(png_ptr, "gray+alpha color-map: too few entries");
2365 cmap_entries = (unsigned int)make_ga_colormap(display);
2367 background_index = PNG_CMAP_GA_BACKGROUND;
2368 output_processing = PNG_CMAP_GA;
2371 else /* alpha is removed */
2373 /* Alpha must be removed as the PNG data is processed when the
2374 * background is a color because the G and A channels are
2375 * independent and the vector addition (non-parallel vectors) is a
2376 * 2-D problem.
2378 * This can be reduced to the same algorithm as above by making a
2379 * colormap containing gray levels (for the opaque grays), a
2380 * background entry (for a transparent pixel) and a set of four six
2381 * level color values, one set for each intermediate alpha value.
2382 * See the comments in make_ga_colormap for how this works in the
2383 * per-pixel processing.
2385 * If the background is gray, however, we only need a 256 entry gray
2386 * level color map. It is sufficient to make the entry generated
2387 * for the background color be exactly the color specified.
2389 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2390 (back_r == back_g && back_g == back_b))
2392 /* Background is gray; no special processing will be required. */
2393 png_color_16 c;
2394 png_uint_32 gray = back_g;
2396 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2397 png_error(png_ptr, "gray-alpha color-map: too few entries");
2399 cmap_entries = (unsigned int)make_gray_colormap(display);
2401 if (output_encoding == P_LINEAR)
2403 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2405 /* And make sure the corresponding palette entry matches. */
2406 png_create_colormap_entry(display, gray, back_g, back_g,
2407 back_g, 65535, P_LINEAR);
2410 /* The background passed to libpng, however, must be the sRGB
2411 * value.
2413 c.index = 0; /*unused*/
2414 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2416 png_set_background_fixed(png_ptr, &c,
2417 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2418 0/*gamma: not used*/);
2420 output_processing = PNG_CMAP_NONE;
2423 else
2425 png_uint_32 i, a;
2427 /* This is the same as png_make_ga_colormap, above, except that
2428 * the entries are all opaque.
2430 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2431 png_error(png_ptr, "ga-alpha color-map: too few entries");
2433 i = 0;
2434 while (i < 231)
2436 png_uint_32 gray = (i * 256 + 115) / 231;
2437 png_create_colormap_entry(display, i++, gray, gray, gray,
2438 255, P_sRGB);
2441 /* NOTE: this preserves the full precision of the application
2442 * background color.
2444 background_index = i;
2445 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2446 #ifdef __COVERITY__
2447 /* Coverity claims that output_encoding
2448 * cannot be 2 (P_LINEAR) here.
2449 */ 255U,
2450 #else
2451 output_encoding == P_LINEAR ? 65535U : 255U,
2452 #endif
2453 output_encoding);
2455 /* For non-opaque input composite on the sRGB background - this
2456 * requires inverting the encoding for each component. The input
2457 * is still converted to the sRGB encoding because this is a
2458 * reasonable approximate to the logarithmic curve of human
2459 * visual sensitivity, at least over the narrow range which PNG
2460 * represents. Consequently 'G' is always sRGB encoded, while
2461 * 'A' is linear. We need the linear background colors.
2463 if (output_encoding == P_sRGB) /* else already linear */
2465 /* This may produce a value not exactly matching the
2466 * background, but that's ok because these numbers are only
2467 * used when alpha != 0
2469 back_r = png_sRGB_table[back_r];
2470 back_g = png_sRGB_table[back_g];
2471 back_b = png_sRGB_table[back_b];
2474 for (a=1; a<5; ++a)
2476 unsigned int g;
2478 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2479 * by an 8-bit alpha value (0..255).
2481 png_uint_32 alpha = 51 * a;
2482 png_uint_32 back_rx = (255-alpha) * back_r;
2483 png_uint_32 back_gx = (255-alpha) * back_g;
2484 png_uint_32 back_bx = (255-alpha) * back_b;
2486 for (g=0; g<6; ++g)
2488 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2490 png_create_colormap_entry(display, i++,
2491 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2492 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2493 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2497 cmap_entries = i;
2498 output_processing = PNG_CMAP_GA;
2501 break;
2503 case PNG_COLOR_TYPE_RGB:
2504 case PNG_COLOR_TYPE_RGB_ALPHA:
2505 /* Exclude the case where the output is gray; we can always handle this
2506 * with the cases above.
2508 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2510 /* The color-map will be grayscale, so we may as well convert the
2511 * input RGB values to a simple grayscale and use the grayscale
2512 * code above.
2514 * NOTE: calling this apparently damages the recognition of the
2515 * transparent color in background color handling; call
2516 * png_set_tRNS_to_alpha before png_set_background_fixed.
2518 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2519 -1);
2520 data_encoding = P_sRGB;
2522 /* The output will now be one or two 8-bit gray or gray+alpha
2523 * channels. The more complex case arises when the input has alpha.
2525 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2526 png_ptr->num_trans > 0) &&
2527 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2529 /* Both input and output have an alpha channel, so no background
2530 * processing is required; just map the GA bytes to the right
2531 * color-map entry.
2533 expand_tRNS = 1;
2535 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2536 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2538 cmap_entries = (unsigned int)make_ga_colormap(display);
2539 background_index = PNG_CMAP_GA_BACKGROUND;
2540 output_processing = PNG_CMAP_GA;
2543 else
2545 /* Either the input or the output has no alpha channel, so there
2546 * will be no non-opaque pixels in the color-map; it will just be
2547 * grayscale.
2549 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2550 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2552 /* Ideally this code would use libpng to do the gamma correction,
2553 * but if an input alpha channel is to be removed we will hit the
2554 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2555 * correction bug). Fix this by dropping the gamma correction in
2556 * this case and doing it in the palette; this will result in
2557 * duplicate palette entries, but that's better than the
2558 * alternative of double gamma correction.
2560 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2561 png_ptr->num_trans > 0) &&
2562 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
2564 cmap_entries = (unsigned int)make_gray_file_colormap(display);
2565 data_encoding = P_FILE;
2568 else
2569 cmap_entries = (unsigned int)make_gray_colormap(display);
2571 /* But if the input has alpha or transparency it must be removed
2573 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2574 png_ptr->num_trans > 0)
2576 png_color_16 c;
2577 png_uint_32 gray = back_g;
2579 /* We need to ensure that the application background exists in
2580 * the colormap and that completely transparent pixels map to
2581 * it. Achieve this simply by ensuring that the entry
2582 * selected for the background really is the background color.
2584 if (data_encoding == P_FILE) /* from the fixup above */
2586 /* The app supplied a gray which is in output_encoding, we
2587 * need to convert it to a value of the input (P_FILE)
2588 * encoding then set this palette entry to the required
2589 * output encoding.
2591 if (output_encoding == P_sRGB)
2592 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2594 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2595 png_ptr->colorspace.gamma)); /* now P_FILE */
2597 /* And make sure the corresponding palette entry contains
2598 * exactly the required sRGB value.
2600 png_create_colormap_entry(display, gray, back_g, back_g,
2601 back_g, 0/*unused*/, output_encoding);
2604 else if (output_encoding == P_LINEAR)
2606 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2608 /* And make sure the corresponding palette entry matches.
2610 png_create_colormap_entry(display, gray, back_g, back_g,
2611 back_g, 0/*unused*/, P_LINEAR);
2614 /* The background passed to libpng, however, must be the
2615 * output (normally sRGB) value.
2617 c.index = 0; /*unused*/
2618 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2620 /* NOTE: the following is apparently a bug in libpng. Without
2621 * it the transparent color recognition in
2622 * png_set_background_fixed seems to go wrong.
2624 expand_tRNS = 1;
2625 png_set_background_fixed(png_ptr, &c,
2626 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2627 0/*gamma: not used*/);
2630 output_processing = PNG_CMAP_NONE;
2634 else /* output is color */
2636 /* We could use png_quantize here so long as there is no transparent
2637 * color or alpha; png_quantize ignores alpha. Easier overall just
2638 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2639 * Consequently we always want libpng to produce sRGB data.
2641 data_encoding = P_sRGB;
2643 /* Is there any transparency or alpha? */
2644 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2645 png_ptr->num_trans > 0)
2647 /* Is there alpha in the output too? If so all four channels are
2648 * processed into a special RGB cube with alpha support.
2650 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2652 png_uint_32 r;
2654 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2655 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2657 cmap_entries = (unsigned int)make_rgb_colormap(display);
2659 /* Add a transparent entry. */
2660 png_create_colormap_entry(display, cmap_entries, 255, 255,
2661 255, 0, P_sRGB);
2663 /* This is stored as the background index for the processing
2664 * algorithm.
2666 background_index = cmap_entries++;
2668 /* Add 27 r,g,b entries each with alpha 0.5. */
2669 for (r=0; r<256; r = (r << 1) | 0x7f)
2671 png_uint_32 g;
2673 for (g=0; g<256; g = (g << 1) | 0x7f)
2675 png_uint_32 b;
2677 /* This generates components with the values 0, 127 and
2678 * 255
2680 for (b=0; b<256; b = (b << 1) | 0x7f)
2681 png_create_colormap_entry(display, cmap_entries++,
2682 r, g, b, 128, P_sRGB);
2686 expand_tRNS = 1;
2687 output_processing = PNG_CMAP_RGB_ALPHA;
2690 else
2692 /* Alpha/transparency must be removed. The background must
2693 * exist in the color map (achieved by setting adding it after
2694 * the 666 color-map). If the standard processing code will
2695 * pick up this entry automatically that's all that is
2696 * required; libpng can be called to do the background
2697 * processing.
2699 unsigned int sample_size =
2700 PNG_IMAGE_SAMPLE_SIZE(output_format);
2701 png_uint_32 r, g, b; /* sRGB background */
2703 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2704 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2706 cmap_entries = (unsigned int)make_rgb_colormap(display);
2708 png_create_colormap_entry(display, cmap_entries, back_r,
2709 back_g, back_b, 0/*unused*/, output_encoding);
2711 if (output_encoding == P_LINEAR)
2713 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2714 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2715 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2718 else
2720 r = back_r;
2721 g = back_g;
2722 b = back_g;
2725 /* Compare the newly-created color-map entry with the one the
2726 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2727 * match, add the new one and set this as the background
2728 * index.
2730 if (memcmp((png_const_bytep)display->colormap +
2731 sample_size * cmap_entries,
2732 (png_const_bytep)display->colormap +
2733 sample_size * PNG_RGB_INDEX(r,g,b),
2734 sample_size) != 0)
2736 /* The background color must be added. */
2737 background_index = cmap_entries++;
2739 /* Add 27 r,g,b entries each with created by composing with
2740 * the background at alpha 0.5.
2742 for (r=0; r<256; r = (r << 1) | 0x7f)
2744 for (g=0; g<256; g = (g << 1) | 0x7f)
2746 /* This generates components with the values 0, 127
2747 * and 255
2749 for (b=0; b<256; b = (b << 1) | 0x7f)
2750 png_create_colormap_entry(display, cmap_entries++,
2751 png_colormap_compose(display, r, P_sRGB, 128,
2752 back_r, output_encoding),
2753 png_colormap_compose(display, g, P_sRGB, 128,
2754 back_g, output_encoding),
2755 png_colormap_compose(display, b, P_sRGB, 128,
2756 back_b, output_encoding),
2757 0/*unused*/, output_encoding);
2761 expand_tRNS = 1;
2762 output_processing = PNG_CMAP_RGB_ALPHA;
2765 else /* background color is in the standard color-map */
2767 png_color_16 c;
2769 c.index = 0; /*unused*/
2770 c.red = (png_uint_16)back_r;
2771 c.gray = c.green = (png_uint_16)back_g;
2772 c.blue = (png_uint_16)back_b;
2774 png_set_background_fixed(png_ptr, &c,
2775 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2776 0/*gamma: not used*/);
2778 output_processing = PNG_CMAP_RGB;
2783 else /* no alpha or transparency in the input */
2785 /* Alpha in the output is irrelevant, simply map the opaque input
2786 * pixels to the 6x6x6 color-map.
2788 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2789 png_error(png_ptr, "rgb color-map: too few entries");
2791 cmap_entries = (unsigned int)make_rgb_colormap(display);
2792 output_processing = PNG_CMAP_RGB;
2795 break;
2797 case PNG_COLOR_TYPE_PALETTE:
2798 /* It's already got a color-map. It may be necessary to eliminate the
2799 * tRNS entries though.
2802 unsigned int num_trans = png_ptr->num_trans;
2803 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2804 png_const_colorp colormap = png_ptr->palette;
2805 int do_background = trans != NULL &&
2806 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2807 unsigned int i;
2809 /* Just in case: */
2810 if (trans == NULL)
2811 num_trans = 0;
2813 output_processing = PNG_CMAP_NONE;
2814 data_encoding = P_FILE; /* Don't change from color-map indices */
2815 cmap_entries = (unsigned int)png_ptr->num_palette;
2816 if (cmap_entries > 256)
2817 cmap_entries = 256;
2819 if (cmap_entries > (unsigned int)image->colormap_entries)
2820 png_error(png_ptr, "palette color-map: too few entries");
2822 for (i=0; i < cmap_entries; ++i)
2824 if (do_background != 0 && i < num_trans && trans[i] < 255)
2826 if (trans[i] == 0)
2827 png_create_colormap_entry(display, i, back_r, back_g,
2828 back_b, 0, output_encoding);
2830 else
2832 /* Must compose the PNG file color in the color-map entry
2833 * on the sRGB color in 'back'.
2835 png_create_colormap_entry(display, i,
2836 png_colormap_compose(display, colormap[i].red,
2837 P_FILE, trans[i], back_r, output_encoding),
2838 png_colormap_compose(display, colormap[i].green,
2839 P_FILE, trans[i], back_g, output_encoding),
2840 png_colormap_compose(display, colormap[i].blue,
2841 P_FILE, trans[i], back_b, output_encoding),
2842 output_encoding == P_LINEAR ? trans[i] * 257U :
2843 trans[i],
2844 output_encoding);
2848 else
2849 png_create_colormap_entry(display, i, colormap[i].red,
2850 colormap[i].green, colormap[i].blue,
2851 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2854 /* The PNG data may have indices packed in fewer than 8 bits, it
2855 * must be expanded if so.
2857 if (png_ptr->bit_depth < 8)
2858 png_set_packing(png_ptr);
2860 break;
2862 default:
2863 png_error(png_ptr, "invalid PNG color type");
2864 /*NOT REACHED*/
2867 /* Now deal with the output processing */
2868 if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
2869 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2870 png_set_tRNS_to_alpha(png_ptr);
2872 switch (data_encoding)
2874 case P_sRGB:
2875 /* Change to 8-bit sRGB */
2876 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2877 /* FALLTHROUGH */
2879 case P_FILE:
2880 if (png_ptr->bit_depth > 8)
2881 png_set_scale_16(png_ptr);
2882 break;
2884 #ifdef __GNUC__
2885 default:
2886 png_error(png_ptr, "bad data option (internal error)");
2887 #endif
2890 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2891 png_error(png_ptr, "color map overflow (BAD internal error)");
2893 image->colormap_entries = cmap_entries;
2895 /* Double check using the recorded background index */
2896 switch (output_processing)
2898 case PNG_CMAP_NONE:
2899 if (background_index != PNG_CMAP_NONE_BACKGROUND)
2900 goto bad_background;
2901 break;
2903 case PNG_CMAP_GA:
2904 if (background_index != PNG_CMAP_GA_BACKGROUND)
2905 goto bad_background;
2906 break;
2908 case PNG_CMAP_TRANS:
2909 if (background_index >= cmap_entries ||
2910 background_index != PNG_CMAP_TRANS_BACKGROUND)
2911 goto bad_background;
2912 break;
2914 case PNG_CMAP_RGB:
2915 if (background_index != PNG_CMAP_RGB_BACKGROUND)
2916 goto bad_background;
2917 break;
2919 case PNG_CMAP_RGB_ALPHA:
2920 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
2921 goto bad_background;
2922 break;
2924 default:
2925 png_error(png_ptr, "bad processing option (internal error)");
2927 bad_background:
2928 png_error(png_ptr, "bad background index (internal error)");
2931 display->colormap_processing = (int)output_processing;
2933 return 1/*ok*/;
2936 /* The final part of the color-map read called from png_image_finish_read. */
2937 static int
2938 png_image_read_and_map(png_voidp argument)
2940 png_image_read_control *display = png_voidcast(png_image_read_control*,
2941 argument);
2942 png_imagep image = display->image;
2943 png_structrp png_ptr = image->opaque->png_ptr;
2944 int passes;
2946 /* Called when the libpng data must be transformed into the color-mapped
2947 * form. There is a local row buffer in display->local and this routine must
2948 * do the interlace handling.
2950 switch (png_ptr->interlaced)
2952 case PNG_INTERLACE_NONE:
2953 passes = 1;
2954 break;
2956 case PNG_INTERLACE_ADAM7:
2957 passes = PNG_INTERLACE_ADAM7_PASSES;
2958 break;
2960 default:
2961 png_error(png_ptr, "unknown interlace type");
2965 png_uint_32 height = image->height;
2966 png_uint_32 width = image->width;
2967 int proc = display->colormap_processing;
2968 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
2969 ptrdiff_t step_row = display->row_bytes;
2970 int pass;
2972 for (pass = 0; pass < passes; ++pass)
2974 unsigned int startx, stepx, stepy;
2975 png_uint_32 y;
2977 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
2979 /* The row may be empty for a short image: */
2980 if (PNG_PASS_COLS(width, pass) == 0)
2981 continue;
2983 startx = PNG_PASS_START_COL(pass);
2984 stepx = PNG_PASS_COL_OFFSET(pass);
2985 y = PNG_PASS_START_ROW(pass);
2986 stepy = PNG_PASS_ROW_OFFSET(pass);
2989 else
2991 y = 0;
2992 startx = 0;
2993 stepx = stepy = 1;
2996 for (; y<height; y += stepy)
2998 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
2999 png_bytep outrow = first_row + y * step_row;
3000 png_const_bytep end_row = outrow + width;
3002 /* Read read the libpng data into the temporary buffer. */
3003 png_read_row(png_ptr, inrow, NULL);
3005 /* Now process the row according to the processing option, note
3006 * that the caller verifies that the format of the libpng output
3007 * data is as required.
3009 outrow += startx;
3010 switch (proc)
3012 case PNG_CMAP_GA:
3013 for (; outrow < end_row; outrow += stepx)
3015 /* The data is always in the PNG order */
3016 unsigned int gray = *inrow++;
3017 unsigned int alpha = *inrow++;
3018 unsigned int entry;
3020 /* NOTE: this code is copied as a comment in
3021 * make_ga_colormap above. Please update the
3022 * comment if you change this code!
3024 if (alpha > 229) /* opaque */
3026 entry = (231 * gray + 128) >> 8;
3028 else if (alpha < 26) /* transparent */
3030 entry = 231;
3032 else /* partially opaque */
3034 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3037 *outrow = (png_byte)entry;
3039 break;
3041 case PNG_CMAP_TRANS:
3042 for (; outrow < end_row; outrow += stepx)
3044 png_byte gray = *inrow++;
3045 png_byte alpha = *inrow++;
3047 if (alpha == 0)
3048 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3050 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3051 *outrow = gray;
3053 else
3054 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3056 break;
3058 case PNG_CMAP_RGB:
3059 for (; outrow < end_row; outrow += stepx)
3061 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3062 inrow += 3;
3064 break;
3066 case PNG_CMAP_RGB_ALPHA:
3067 for (; outrow < end_row; outrow += stepx)
3069 unsigned int alpha = inrow[3];
3071 /* Because the alpha entries only hold alpha==0.5 values
3072 * split the processing at alpha==0.25 (64) and 0.75
3073 * (196).
3076 if (alpha >= 196)
3077 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3078 inrow[2]);
3080 else if (alpha < 64)
3081 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3083 else
3085 /* Likewise there are three entries for each of r, g
3086 * and b. We could select the entry by popcount on
3087 * the top two bits on those architectures that
3088 * support it, this is what the code below does,
3089 * crudely.
3091 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3093 /* Here are how the values map:
3095 * 0x00 .. 0x3f -> 0
3096 * 0x40 .. 0xbf -> 1
3097 * 0xc0 .. 0xff -> 2
3099 * So, as above with the explicit alpha checks, the
3100 * breakpoints are at 64 and 196.
3102 if (inrow[0] & 0x80) back_i += 9; /* red */
3103 if (inrow[0] & 0x40) back_i += 9;
3104 if (inrow[0] & 0x80) back_i += 3; /* green */
3105 if (inrow[0] & 0x40) back_i += 3;
3106 if (inrow[0] & 0x80) back_i += 1; /* blue */
3107 if (inrow[0] & 0x40) back_i += 1;
3109 *outrow = (png_byte)back_i;
3112 inrow += 4;
3114 break;
3116 default:
3117 break;
3123 return 1;
3126 static int
3127 png_image_read_colormapped(png_voidp argument)
3129 png_image_read_control *display = png_voidcast(png_image_read_control*,
3130 argument);
3131 png_imagep image = display->image;
3132 png_controlp control = image->opaque;
3133 png_structrp png_ptr = control->png_ptr;
3134 png_inforp info_ptr = control->info_ptr;
3136 int passes = 0; /* As a flag */
3138 PNG_SKIP_CHUNKS(png_ptr);
3140 /* Update the 'info' structure and make sure the result is as required; first
3141 * make sure to turn on the interlace handling if it will be required
3142 * (because it can't be turned on *after* the call to png_read_update_info!)
3144 if (display->colormap_processing == PNG_CMAP_NONE)
3145 passes = png_set_interlace_handling(png_ptr);
3147 png_read_update_info(png_ptr, info_ptr);
3149 /* The expected output can be deduced from the colormap_processing option. */
3150 switch (display->colormap_processing)
3152 case PNG_CMAP_NONE:
3153 /* Output must be one channel and one byte per pixel, the output
3154 * encoding can be anything.
3156 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3157 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3158 info_ptr->bit_depth == 8)
3159 break;
3161 goto bad_output;
3163 case PNG_CMAP_TRANS:
3164 case PNG_CMAP_GA:
3165 /* Output must be two channels and the 'G' one must be sRGB, the latter
3166 * can be checked with an exact number because it should have been set
3167 * to this number above!
3169 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3170 info_ptr->bit_depth == 8 &&
3171 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3172 image->colormap_entries == 256)
3173 break;
3175 goto bad_output;
3177 case PNG_CMAP_RGB:
3178 /* Output must be 8-bit sRGB encoded RGB */
3179 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3180 info_ptr->bit_depth == 8 &&
3181 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3182 image->colormap_entries == 216)
3183 break;
3185 goto bad_output;
3187 case PNG_CMAP_RGB_ALPHA:
3188 /* Output must be 8-bit sRGB encoded RGBA */
3189 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3190 info_ptr->bit_depth == 8 &&
3191 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3192 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3193 break;
3195 goto bad_output;
3197 default:
3198 bad_output:
3199 png_error(png_ptr, "bad color-map processing (internal error)");
3202 /* Now read the rows. Do this here if it is possible to read directly into
3203 * the output buffer, otherwise allocate a local row buffer of the maximum
3204 * size libpng requires and call the relevant processing routine safely.
3207 png_voidp first_row = display->buffer;
3208 ptrdiff_t row_bytes = display->row_stride;
3210 /* The following expression is designed to work correctly whether it gives
3211 * a signed or an unsigned result.
3213 if (row_bytes < 0)
3215 char *ptr = png_voidcast(char*, first_row);
3216 ptr += (image->height-1) * (-row_bytes);
3217 first_row = png_voidcast(png_voidp, ptr);
3220 display->first_row = first_row;
3221 display->row_bytes = row_bytes;
3224 if (passes == 0)
3226 int result;
3227 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3229 display->local_row = row;
3230 result = png_safe_execute(image, png_image_read_and_map, display);
3231 display->local_row = NULL;
3232 png_free(png_ptr, row);
3234 return result;
3237 else
3239 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
3241 while (--passes >= 0)
3243 png_uint_32 y = image->height;
3244 png_bytep row = png_voidcast(png_bytep, display->first_row);
3246 for (; y > 0; --y)
3248 png_read_row(png_ptr, row, NULL);
3249 row += row_bytes;
3253 return 1;
3257 /* Just the row reading part of png_image_read. */
3258 static int
3259 png_image_read_composite(png_voidp argument)
3261 png_image_read_control *display = png_voidcast(png_image_read_control*,
3262 argument);
3263 png_imagep image = display->image;
3264 png_structrp png_ptr = image->opaque->png_ptr;
3265 int passes;
3267 switch (png_ptr->interlaced)
3269 case PNG_INTERLACE_NONE:
3270 passes = 1;
3271 break;
3273 case PNG_INTERLACE_ADAM7:
3274 passes = PNG_INTERLACE_ADAM7_PASSES;
3275 break;
3277 default:
3278 png_error(png_ptr, "unknown interlace type");
3282 png_uint_32 height = image->height;
3283 png_uint_32 width = image->width;
3284 ptrdiff_t step_row = display->row_bytes;
3285 unsigned int channels =
3286 (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
3287 int pass;
3289 for (pass = 0; pass < passes; ++pass)
3291 unsigned int startx, stepx, stepy;
3292 png_uint_32 y;
3294 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3296 /* The row may be empty for a short image: */
3297 if (PNG_PASS_COLS(width, pass) == 0)
3298 continue;
3300 startx = PNG_PASS_START_COL(pass) * channels;
3301 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3302 y = PNG_PASS_START_ROW(pass);
3303 stepy = PNG_PASS_ROW_OFFSET(pass);
3306 else
3308 y = 0;
3309 startx = 0;
3310 stepx = channels;
3311 stepy = 1;
3314 for (; y<height; y += stepy)
3316 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3317 png_bytep outrow;
3318 png_const_bytep end_row;
3320 /* Read the row, which is packed: */
3321 png_read_row(png_ptr, inrow, NULL);
3323 outrow = png_voidcast(png_bytep, display->first_row);
3324 outrow += y * step_row;
3325 end_row = outrow + width * channels;
3327 /* Now do the composition on each pixel in this row. */
3328 outrow += startx;
3329 for (; outrow < end_row; outrow += stepx)
3331 png_byte alpha = inrow[channels];
3333 if (alpha > 0) /* else no change to the output */
3335 unsigned int c;
3337 for (c=0; c<channels; ++c)
3339 png_uint_32 component = inrow[c];
3341 if (alpha < 255) /* else just use component */
3343 /* This is PNG_OPTIMIZED_ALPHA, the component value
3344 * is a linear 8-bit value. Combine this with the
3345 * current outrow[c] value which is sRGB encoded.
3346 * Arithmetic here is 16-bits to preserve the output
3347 * values correctly.
3349 component *= 257*255; /* =65535 */
3350 component += (255-alpha)*png_sRGB_table[outrow[c]];
3352 /* So 'component' is scaled by 255*65535 and is
3353 * therefore appropriate for the sRGB to linear
3354 * conversion table.
3356 component = PNG_sRGB_FROM_LINEAR(component);
3359 outrow[c] = (png_byte)component;
3363 inrow += channels+1; /* components and alpha channel */
3369 return 1;
3372 /* The do_local_background case; called when all the following transforms are to
3373 * be done:
3375 * PNG_RGB_TO_GRAY
3376 * PNG_COMPOSITE
3377 * PNG_GAMMA
3379 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
3380 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3381 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from
3382 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
3383 * row and handles the removal or pre-multiplication of the alpha channel.
3385 static int
3386 png_image_read_background(png_voidp argument)
3388 png_image_read_control *display = png_voidcast(png_image_read_control*,
3389 argument);
3390 png_imagep image = display->image;
3391 png_structrp png_ptr = image->opaque->png_ptr;
3392 png_inforp info_ptr = image->opaque->info_ptr;
3393 png_uint_32 height = image->height;
3394 png_uint_32 width = image->width;
3395 int pass, passes;
3397 /* Double check the convoluted logic below. We expect to get here with
3398 * libpng doing rgb to gray and gamma correction but background processing
3399 * left to the png_image_read_background function. The rows libpng produce
3400 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3402 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3403 png_error(png_ptr, "lost rgb to gray");
3405 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3406 png_error(png_ptr, "unexpected compose");
3408 if (png_get_channels(png_ptr, info_ptr) != 2)
3409 png_error(png_ptr, "lost/gained channels");
3411 /* Expect the 8-bit case to always remove the alpha channel */
3412 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3413 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3414 png_error(png_ptr, "unexpected 8-bit transformation");
3416 switch (png_ptr->interlaced)
3418 case PNG_INTERLACE_NONE:
3419 passes = 1;
3420 break;
3422 case PNG_INTERLACE_ADAM7:
3423 passes = PNG_INTERLACE_ADAM7_PASSES;
3424 break;
3426 default:
3427 png_error(png_ptr, "unknown interlace type");
3430 /* Use direct access to info_ptr here because otherwise the simplified API
3431 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3432 * checking the value after libpng expansions, not the original value in the
3433 * PNG.
3435 switch (info_ptr->bit_depth)
3437 case 8:
3438 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3439 * to be removed by composing on a background: either the row if
3440 * display->background is NULL or display->background->green if not.
3441 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3444 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3445 ptrdiff_t step_row = display->row_bytes;
3447 for (pass = 0; pass < passes; ++pass)
3449 png_bytep row = png_voidcast(png_bytep, display->first_row);
3450 unsigned int startx, stepx, stepy;
3451 png_uint_32 y;
3453 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3455 /* The row may be empty for a short image: */
3456 if (PNG_PASS_COLS(width, pass) == 0)
3457 continue;
3459 startx = PNG_PASS_START_COL(pass);
3460 stepx = PNG_PASS_COL_OFFSET(pass);
3461 y = PNG_PASS_START_ROW(pass);
3462 stepy = PNG_PASS_ROW_OFFSET(pass);
3465 else
3467 y = 0;
3468 startx = 0;
3469 stepx = stepy = 1;
3472 if (display->background == NULL)
3474 for (; y<height; y += stepy)
3476 png_bytep inrow = png_voidcast(png_bytep,
3477 display->local_row);
3478 png_bytep outrow = first_row + y * step_row;
3479 png_const_bytep end_row = outrow + width;
3481 /* Read the row, which is packed: */
3482 png_read_row(png_ptr, inrow, NULL);
3484 /* Now do the composition on each pixel in this row. */
3485 outrow += startx;
3486 for (; outrow < end_row; outrow += stepx)
3488 png_byte alpha = inrow[1];
3490 if (alpha > 0) /* else no change to the output */
3492 png_uint_32 component = inrow[0];
3494 if (alpha < 255) /* else just use component */
3496 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3497 * necessary to invert the sRGB transfer
3498 * function and multiply the alpha out.
3500 component = png_sRGB_table[component] * alpha;
3501 component += png_sRGB_table[outrow[0]] *
3502 (255-alpha);
3503 component = PNG_sRGB_FROM_LINEAR(component);
3506 outrow[0] = (png_byte)component;
3509 inrow += 2; /* gray and alpha channel */
3514 else /* constant background value */
3516 png_byte background8 = display->background->green;
3517 png_uint_16 background = png_sRGB_table[background8];
3519 for (; y<height; y += stepy)
3521 png_bytep inrow = png_voidcast(png_bytep,
3522 display->local_row);
3523 png_bytep outrow = first_row + y * step_row;
3524 png_const_bytep end_row = outrow + width;
3526 /* Read the row, which is packed: */
3527 png_read_row(png_ptr, inrow, NULL);
3529 /* Now do the composition on each pixel in this row. */
3530 outrow += startx;
3531 for (; outrow < end_row; outrow += stepx)
3533 png_byte alpha = inrow[1];
3535 if (alpha > 0) /* else use background */
3537 png_uint_32 component = inrow[0];
3539 if (alpha < 255) /* else just use component */
3541 component = png_sRGB_table[component] * alpha;
3542 component += background * (255-alpha);
3543 component = PNG_sRGB_FROM_LINEAR(component);
3546 outrow[0] = (png_byte)component;
3549 else
3550 outrow[0] = background8;
3552 inrow += 2; /* gray and alpha channel */
3555 row += display->row_bytes;
3560 break;
3562 case 16:
3563 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3564 * still be done and, maybe, the alpha channel removed. This code also
3565 * handles the alpha-first option.
3568 png_uint_16p first_row = png_voidcast(png_uint_16p,
3569 display->first_row);
3570 /* The division by two is safe because the caller passed in a
3571 * stride which was multiplied by 2 (below) to get row_bytes.
3573 ptrdiff_t step_row = display->row_bytes / 2;
3574 unsigned int preserve_alpha = (image->format &
3575 PNG_FORMAT_FLAG_ALPHA) != 0;
3576 unsigned int outchannels = 1U+preserve_alpha;
3577 int swap_alpha = 0;
3579 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3580 if (preserve_alpha != 0 &&
3581 (image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
3582 swap_alpha = 1;
3583 # endif
3585 for (pass = 0; pass < passes; ++pass)
3587 unsigned int startx, stepx, stepy;
3588 png_uint_32 y;
3590 /* The 'x' start and step are adjusted to output components here.
3592 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3594 /* The row may be empty for a short image: */
3595 if (PNG_PASS_COLS(width, pass) == 0)
3596 continue;
3598 startx = PNG_PASS_START_COL(pass) * outchannels;
3599 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3600 y = PNG_PASS_START_ROW(pass);
3601 stepy = PNG_PASS_ROW_OFFSET(pass);
3604 else
3606 y = 0;
3607 startx = 0;
3608 stepx = outchannels;
3609 stepy = 1;
3612 for (; y<height; y += stepy)
3614 png_const_uint_16p inrow;
3615 png_uint_16p outrow = first_row + y*step_row;
3616 png_uint_16p end_row = outrow + width * outchannels;
3618 /* Read the row, which is packed: */
3619 png_read_row(png_ptr, png_voidcast(png_bytep,
3620 display->local_row), NULL);
3621 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3623 /* Now do the pre-multiplication on each pixel in this row.
3625 outrow += startx;
3626 for (; outrow < end_row; outrow += stepx)
3628 png_uint_32 component = inrow[0];
3629 png_uint_16 alpha = inrow[1];
3631 if (alpha > 0) /* else 0 */
3633 if (alpha < 65535) /* else just use component */
3635 component *= alpha;
3636 component += 32767;
3637 component /= 65535;
3641 else
3642 component = 0;
3644 outrow[swap_alpha] = (png_uint_16)component;
3645 if (preserve_alpha != 0)
3646 outrow[1 ^ swap_alpha] = alpha;
3648 inrow += 2; /* components and alpha channel */
3653 break;
3655 #ifdef __GNUC__
3656 default:
3657 png_error(png_ptr, "unexpected bit depth");
3658 #endif
3661 return 1;
3664 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3665 static int
3666 png_image_read_direct(png_voidp argument)
3668 png_image_read_control *display = png_voidcast(png_image_read_control*,
3669 argument);
3670 png_imagep image = display->image;
3671 png_structrp png_ptr = image->opaque->png_ptr;
3672 png_inforp info_ptr = image->opaque->info_ptr;
3674 png_uint_32 format = image->format;
3675 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3676 int do_local_compose = 0;
3677 int do_local_background = 0; /* to avoid double gamma correction bug */
3678 int passes = 0;
3680 /* Add transforms to ensure the correct output format is produced then check
3681 * that the required implementation support is there. Always expand; always
3682 * need 8 bits minimum, no palette and expanded tRNS.
3684 png_set_expand(png_ptr);
3686 /* Now check the format to see if it was modified. */
3688 png_uint_32 base_format = png_image_format(png_ptr) &
3689 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3690 png_uint_32 change = format ^ base_format;
3691 png_fixed_point output_gamma;
3692 int mode; /* alpha mode */
3694 /* Do this first so that we have a record if rgb to gray is happening. */
3695 if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
3697 /* gray<->color transformation required. */
3698 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3699 png_set_gray_to_rgb(png_ptr);
3701 else
3703 /* libpng can't do both rgb to gray and
3704 * background/pre-multiplication if there is also significant gamma
3705 * correction, because both operations require linear colors and
3706 * the code only supports one transform doing the gamma correction.
3707 * Handle this by doing the pre-multiplication or background
3708 * operation in this code, if necessary.
3710 * TODO: fix this by rewriting pngrtran.c (!)
3712 * For the moment (given that fixing this in pngrtran.c is an
3713 * enormous change) 'do_local_background' is used to indicate that
3714 * the problem exists.
3716 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3717 do_local_background = 1/*maybe*/;
3719 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3720 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3723 change &= ~PNG_FORMAT_FLAG_COLOR;
3726 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3729 png_fixed_point input_gamma_default;
3731 if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 &&
3732 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3733 input_gamma_default = PNG_GAMMA_LINEAR;
3734 else
3735 input_gamma_default = PNG_DEFAULT_sRGB;
3737 /* Call png_set_alpha_mode to set the default for the input gamma; the
3738 * output gamma is set by a second call below.
3740 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3743 if (linear != 0)
3745 /* If there *is* an alpha channel in the input it must be multiplied
3746 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3748 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3749 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3751 else
3752 mode = PNG_ALPHA_PNG;
3754 output_gamma = PNG_GAMMA_LINEAR;
3757 else
3759 mode = PNG_ALPHA_PNG;
3760 output_gamma = PNG_DEFAULT_sRGB;
3763 if ((change & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0)
3765 mode = PNG_ALPHA_OPTIMIZED;
3766 change &= ~PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
3769 /* If 'do_local_background' is set check for the presence of gamma
3770 * correction; this is part of the work-round for the libpng bug
3771 * described above.
3773 * TODO: fix libpng and remove this.
3775 if (do_local_background != 0)
3777 png_fixed_point gtest;
3779 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3780 * gamma correction, the screen gamma hasn't been set on png_struct
3781 * yet; it's set below. png_struct::gamma, however, is set to the
3782 * final value.
3784 if (png_muldiv(&gtest, output_gamma, png_ptr->colorspace.gamma,
3785 PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
3786 do_local_background = 0;
3788 else if (mode == PNG_ALPHA_STANDARD)
3790 do_local_background = 2/*required*/;
3791 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3794 /* else leave as 1 for the checks below */
3797 /* If the bit-depth changes then handle that here. */
3798 if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
3800 if (linear != 0 /*16-bit output*/)
3801 png_set_expand_16(png_ptr);
3803 else /* 8-bit output */
3804 png_set_scale_16(png_ptr);
3806 change &= ~PNG_FORMAT_FLAG_LINEAR;
3809 /* Now the background/alpha channel changes. */
3810 if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
3812 /* Removing an alpha channel requires composition for the 8-bit
3813 * formats; for the 16-bit it is already done, above, by the
3814 * pre-multiplication and the channel just needs to be stripped.
3816 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3818 /* If RGB->gray is happening the alpha channel must be left and the
3819 * operation completed locally.
3821 * TODO: fix libpng and remove this.
3823 if (do_local_background != 0)
3824 do_local_background = 2/*required*/;
3826 /* 16-bit output: just remove the channel */
3827 else if (linear != 0) /* compose on black (well, pre-multiply) */
3828 png_set_strip_alpha(png_ptr);
3830 /* 8-bit output: do an appropriate compose */
3831 else if (display->background != NULL)
3833 png_color_16 c;
3835 c.index = 0; /*unused*/
3836 c.red = display->background->red;
3837 c.green = display->background->green;
3838 c.blue = display->background->blue;
3839 c.gray = display->background->green;
3841 /* This is always an 8-bit sRGB value, using the 'green' channel
3842 * for gray is much better than calculating the luminance here;
3843 * we can get off-by-one errors in that calculation relative to
3844 * the app expectations and that will show up in transparent
3845 * pixels.
3847 png_set_background_fixed(png_ptr, &c,
3848 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3849 0/*gamma: not used*/);
3852 else /* compose on row: implemented below. */
3854 do_local_compose = 1;
3855 /* This leaves the alpha channel in the output, so it has to be
3856 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3857 * one so the code only has to hack on the pixels that require
3858 * composition.
3860 mode = PNG_ALPHA_OPTIMIZED;
3864 else /* output needs an alpha channel */
3866 /* This is tricky because it happens before the swap operation has
3867 * been accomplished; however, the swap does *not* swap the added
3868 * alpha channel (weird API), so it must be added in the correct
3869 * place.
3871 png_uint_32 filler; /* opaque filler */
3872 int where;
3874 if (linear != 0)
3875 filler = 65535;
3877 else
3878 filler = 255;
3880 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
3881 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3883 where = PNG_FILLER_BEFORE;
3884 change &= ~PNG_FORMAT_FLAG_AFIRST;
3887 else
3888 #endif
3889 where = PNG_FILLER_AFTER;
3891 png_set_add_alpha(png_ptr, filler, where);
3894 /* This stops the (irrelevant) call to swap_alpha below. */
3895 change &= ~PNG_FORMAT_FLAG_ALPHA;
3898 /* Now set the alpha mode correctly; this is always done, even if there is
3899 * no alpha channel in either the input or the output because it correctly
3900 * sets the output gamma.
3902 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
3904 # ifdef PNG_FORMAT_BGR_SUPPORTED
3905 if ((change & PNG_FORMAT_FLAG_BGR) != 0)
3907 /* Check only the output format; PNG is never BGR; don't do this if
3908 * the output is gray, but fix up the 'format' value in that case.
3910 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3911 png_set_bgr(png_ptr);
3913 else
3914 format &= ~PNG_FORMAT_FLAG_BGR;
3916 change &= ~PNG_FORMAT_FLAG_BGR;
3918 # endif
3920 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3921 if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
3923 /* Only relevant if there is an alpha channel - it's particularly
3924 * important to handle this correctly because do_local_compose may
3925 * be set above and then libpng will keep the alpha channel for this
3926 * code to remove.
3928 if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
3930 /* Disable this if doing a local background,
3931 * TODO: remove this when local background is no longer required.
3933 if (do_local_background != 2)
3934 png_set_swap_alpha(png_ptr);
3937 else
3938 format &= ~PNG_FORMAT_FLAG_AFIRST;
3940 change &= ~PNG_FORMAT_FLAG_AFIRST;
3942 # endif
3944 /* If the *output* is 16-bit then we need to check for a byte-swap on this
3945 * architecture.
3947 if (linear != 0)
3949 png_uint_16 le = 0x0001;
3951 if ((*(png_const_bytep) & le) != 0)
3952 png_set_swap(png_ptr);
3955 /* If change is not now 0 some transformation is missing - error out. */
3956 if (change != 0)
3957 png_error(png_ptr, "png_read_image: unsupported transformation");
3960 PNG_SKIP_CHUNKS(png_ptr);
3962 /* Update the 'info' structure and make sure the result is as required; first
3963 * make sure to turn on the interlace handling if it will be required
3964 * (because it can't be turned on *after* the call to png_read_update_info!)
3966 * TODO: remove the do_local_background fixup below.
3968 if (do_local_compose == 0 && do_local_background != 2)
3969 passes = png_set_interlace_handling(png_ptr);
3971 png_read_update_info(png_ptr, info_ptr);
3974 png_uint_32 info_format = 0;
3976 if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
3977 info_format |= PNG_FORMAT_FLAG_COLOR;
3979 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
3981 /* do_local_compose removes this channel below. */
3982 if (do_local_compose == 0)
3984 /* do_local_background does the same if required. */
3985 if (do_local_background != 2 ||
3986 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
3987 info_format |= PNG_FORMAT_FLAG_ALPHA;
3991 else if (do_local_compose != 0) /* internal error */
3992 png_error(png_ptr, "png_image_read: alpha channel lost");
3994 if ((format & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0) {
3995 info_format |= PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
3998 if (info_ptr->bit_depth == 16)
3999 info_format |= PNG_FORMAT_FLAG_LINEAR;
4001 #ifdef PNG_FORMAT_BGR_SUPPORTED
4002 if ((png_ptr->transformations & PNG_BGR) != 0)
4003 info_format |= PNG_FORMAT_FLAG_BGR;
4004 #endif
4006 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
4007 if (do_local_background == 2)
4009 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
4010 info_format |= PNG_FORMAT_FLAG_AFIRST;
4013 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
4014 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
4015 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
4017 if (do_local_background == 2)
4018 png_error(png_ptr, "unexpected alpha swap transformation");
4020 info_format |= PNG_FORMAT_FLAG_AFIRST;
4022 # endif
4024 /* This is actually an internal error. */
4025 if (info_format != format)
4026 png_error(png_ptr, "png_read_image: invalid transformations");
4029 /* Now read the rows. If do_local_compose is set then it is necessary to use
4030 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4031 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4032 * display acts as a flag.
4035 png_voidp first_row = display->buffer;
4036 ptrdiff_t row_bytes = display->row_stride;
4038 if (linear != 0)
4039 row_bytes *= 2;
4041 /* The following expression is designed to work correctly whether it gives
4042 * a signed or an unsigned result.
4044 if (row_bytes < 0)
4046 char *ptr = png_voidcast(char*, first_row);
4047 ptr += (image->height-1) * (-row_bytes);
4048 first_row = png_voidcast(png_voidp, ptr);
4051 display->first_row = first_row;
4052 display->row_bytes = row_bytes;
4055 if (do_local_compose != 0)
4057 int result;
4058 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4060 display->local_row = row;
4061 result = png_safe_execute(image, png_image_read_composite, display);
4062 display->local_row = NULL;
4063 png_free(png_ptr, row);
4065 return result;
4068 else if (do_local_background == 2)
4070 int result;
4071 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4073 display->local_row = row;
4074 result = png_safe_execute(image, png_image_read_background, display);
4075 display->local_row = NULL;
4076 png_free(png_ptr, row);
4078 return result;
4081 else
4083 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
4085 while (--passes >= 0)
4087 png_uint_32 y = image->height;
4088 png_bytep row = png_voidcast(png_bytep, display->first_row);
4090 for (; y > 0; --y)
4092 png_read_row(png_ptr, row, NULL);
4093 row += row_bytes;
4097 return 1;
4101 int PNGAPI
4102 png_image_finish_read(png_imagep image, png_const_colorp background,
4103 void *buffer, png_int_32 row_stride, void *colormap)
4105 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4107 /* Check for row_stride overflow. This check is not performed on the
4108 * original PNG format because it may not occur in the output PNG format
4109 * and libpng deals with the issues of reading the original.
4111 unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
4113 /* The following checks just the 'row_stride' calculation to ensure it
4114 * fits in a signed 32-bit value. Because channels/components can be
4115 * either 1 or 2 bytes in size the length of a row can still overflow 32
4116 * bits; this is just to verify that the 'row_stride' argument can be
4117 * represented.
4119 if (image->width <= 0x7fffffffU/channels) /* no overflow */
4121 png_uint_32 check;
4122 png_uint_32 png_row_stride = image->width * channels;
4124 if (row_stride == 0)
4125 row_stride = (png_int_32)/*SAFE*/png_row_stride;
4127 if (row_stride < 0)
4128 check = (png_uint_32)(-row_stride);
4130 else
4131 check = (png_uint_32)row_stride;
4133 /* This verifies 'check', the absolute value of the actual stride
4134 * passed in and detects overflow in the application calculation (i.e.
4135 * if the app did actually pass in a non-zero 'row_stride'.
4137 if (image->opaque != NULL && buffer != NULL && check >= png_row_stride)
4139 /* Now check for overflow of the image buffer calculation; this
4140 * limits the whole image size to 32 bits for API compatibility with
4141 * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro.
4143 * The PNG_IMAGE_BUFFER_SIZE macro is:
4145 * (PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)*height*(row_stride))
4147 * And the component size is always 1 or 2, so make sure that the
4148 * number of *bytes* that the application is saying are available
4149 * does actually fit into a 32-bit number.
4151 * NOTE: this will be changed in 1.7 because PNG_IMAGE_BUFFER_SIZE
4152 * will be changed to use png_alloc_size_t; bigger images can be
4153 * accommodated on 64-bit systems.
4155 if (image->height <=
4156 0xffffffffU/PNG_IMAGE_PIXEL_COMPONENT_SIZE(image->format)/check)
4158 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4159 (image->colormap_entries > 0 && colormap != NULL))
4161 int result;
4162 png_image_read_control display;
4164 memset(&display, 0, (sizeof display));
4165 display.image = image;
4166 display.buffer = buffer;
4167 display.row_stride = row_stride;
4168 display.colormap = colormap;
4169 display.background = background;
4170 display.local_row = NULL;
4172 /* Choose the correct 'end' routine; for the color-map case
4173 * all the setup has already been done.
4175 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
4176 result =
4177 png_safe_execute(image,
4178 png_image_read_colormap, &display) &&
4179 png_safe_execute(image,
4180 png_image_read_colormapped, &display);
4182 else
4183 result =
4184 png_safe_execute(image,
4185 png_image_read_direct, &display);
4187 png_image_free(image);
4188 return result;
4191 else
4192 return png_image_error(image,
4193 "png_image_finish_read[color-map]: no color-map");
4196 else
4197 return png_image_error(image,
4198 "png_image_finish_read: image too large");
4201 else
4202 return png_image_error(image,
4203 "png_image_finish_read: invalid argument");
4206 else
4207 return png_image_error(image,
4208 "png_image_finish_read: row_stride too large");
4211 else if (image != NULL)
4212 return png_image_error(image,
4213 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4215 return 0;
4218 #endif /* SIMPLIFIED_READ */
4219 #endif /* READ */