compiler/libjpeg/test/wrgif.c

   1 /*
   2     $Id$
   3 */
   4
   5 /*
   6  * wrgif.c
   7  *
   8  * Copyright (C) 1991-1997, Thomas G. Lane.
   9  * This file is part of the Independent JPEG Group's software.
  10  * For conditions of distribution and use, see the accompanying README file.
  11  *
  12  * This file contains routines to write output images in GIF format.
  13  *
  14  **************************************************************************
  15  * NOTE: to avoid entanglements with Unisys' patent on LZW compression,   *
  16  * this code has been modified to output "uncompressed GIF" files.        *
  17  * There is no trace of the LZW algorithm in this file.                   *
  18  **************************************************************************
  19  *
  20  * These routines may need modification for non-Unix environments or
  21  * specialized applications.  As they stand, they assume output to
  22  * an ordinary stdio stream.
  23  */
  24
  25 /*
  26  * This code is loosely based on ppmtogif from the PBMPLUS distribution
  27  * of Feb. 1991.  That file contains the following copyright notice:
  28  *    Based on GIFENCODE by David Rowley <mgardi@watdscu.waterloo.edu>.
  29  *    Lempel-Ziv compression based on "compress" by Spencer W. Thomas et al.
  30  *    Copyright (C) 1989 by Jef Poskanzer.
  31  *    Permission to use, copy, modify, and distribute this software and its
  32  *    documentation for any purpose and without fee is hereby granted, provided
  33  *    that the above copyright notice appear in all copies and that both that
  34  *    copyright notice and this permission notice appear in supporting
  35  *    documentation.  This software is provided "as is" without express or
  36  *    implied warranty.
  37  *
  38  * We are also required to state that
  39  *    "The Graphics Interchange Format(c) is the Copyright property of
  40  *    CompuServe Incorporated. GIF(sm) is a Service Mark property of
  41  *    CompuServe Incorporated."
  42  */
  43
  44 #include "cdjpeg.h"             /* Common decls for cjpeg/djpeg applications */
  45
  46 #ifdef GIF_SUPPORTED
  47
  48
  49 /* Private version of data destination object */
  50
  51 typedef struct {
  52   struct djpeg_dest_struct pub; /* public fields */
  53
  54   j_decompress_ptr cinfo;       /* back link saves passing separate parm */
  55
  56   /* State for packing variable-width codes into a bitstream */
  57   int n_bits;                   /* current number of bits/code */
  58   int maxcode;                  /* maximum code, given n_bits */
  59   INT32 cur_accum;              /* holds bits not yet output */
  60   int cur_bits;                 /* # of bits in cur_accum */
  61
  62   /* State for GIF code assignment */
  63   int ClearCode;                /* clear code (doesn't change) */
  64   int EOFCode;                  /* EOF code (ditto) */
  65   int code_counter;             /* counts output symbols */
  66
  67   /* GIF data packet construction buffer */
  68   int bytesinpkt;               /* # of bytes in current packet */
  69   char packetbuf[256];          /* workspace for accumulating packet */
  70
  71 } gif_dest_struct;
  72
  73 typedef gif_dest_struct * gif_dest_ptr;
  74
  75 /* Largest value that will fit in N bits */
  76 #define MAXCODE(n_bits) ((1 << (n_bits)) - 1)
  77
  78
  79 /*
  80  * Routines to package finished data bytes into GIF data blocks.
  81  * A data block consists of a count byte (1..255) and that many data bytes.
  82  */
  83
  84 LOCAL(void)
  85 flush_packet (gif_dest_ptr dinfo)
  86 /* flush any accumulated data */
  87 {
  88   if (dinfo->bytesinpkt > 0) {  /* never write zero-length packet */
  89     dinfo->packetbuf[0] = (char) dinfo->bytesinpkt++;
  90     if (JFWRITE(dinfo->pub.output_file, dinfo->packetbuf, dinfo->bytesinpkt)
  91         != (size_t) dinfo->bytesinpkt)
  92       ERREXIT(dinfo->cinfo, JERR_FILE_WRITE);
  93     dinfo->bytesinpkt = 0;
  94   }
  95 }
  96
  97
  98 /* Add a character to current packet; flush to disk if necessary */
  99 #define CHAR_OUT(dinfo,c)  \
 100         { (dinfo)->packetbuf[++(dinfo)->bytesinpkt] = (char) (c);  \
 101             if ((dinfo)->bytesinpkt >= 255)  \
 102               flush_packet(dinfo);  \
 103         }
 104
 105
 106 /* Routine to convert variable-width codes into a byte stream */
 107
 108 LOCAL(void)
 109 output (gif_dest_ptr dinfo, int code)
 110 /* Emit a code of n_bits bits */
 111 /* Uses cur_accum and cur_bits to reblock into 8-bit bytes */
 112 {
 113   dinfo->cur_accum |= ((INT32) code) << dinfo->cur_bits;
 114   dinfo->cur_bits += dinfo->n_bits;
 115
 116   while (dinfo->cur_bits >= 8) {
 117     CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF);
 118     dinfo->cur_accum >>= 8;
 119     dinfo->cur_bits -= 8;
 120   }
 121 }
 122
 123
 124 /* The pseudo-compression algorithm.
 125  *
 126  * In this module we simply output each pixel value as a separate symbol;
 127  * thus, no compression occurs.  In fact, there is expansion of one bit per
 128  * pixel, because we use a symbol width one bit wider than the pixel width.
 129  *
 130  * GIF ordinarily uses variable-width symbols, and the decoder will expect
 131  * to ratchet up the symbol width after a fixed number of symbols.
 132  * To simplify the logic and keep the expansion penalty down, we emit a
 133  * GIF Clear code to reset the decoder just before the width would ratchet up.
 134  * Thus, all the symbols in the output file will have the same bit width.
 135  * Note that emitting the Clear codes at the right times is a mere matter of
 136  * counting output symbols and is in no way dependent on the LZW patent.
 137  *
 138  * With a small basic pixel width (low color count), Clear codes will be
 139  * needed very frequently, causing the file to expand even more.  So this
 140  * simplistic approach wouldn't work too well on bilevel images, for example.
 141  * But for output of JPEG conversions the pixel width will usually be 8 bits
 142  * (129 to 256 colors), so the overhead added by Clear symbols is only about
 143  * one symbol in every 256.
 144  */
 145
 146 LOCAL(void)
 147 compress_init (gif_dest_ptr dinfo, int i_bits)
 148 /* Initialize pseudo-compressor */
 149 {
 150   /* init all the state variables */
 151   dinfo->n_bits = i_bits;
 152   dinfo->maxcode = MAXCODE(dinfo->n_bits);
 153   dinfo->ClearCode = (1 << (i_bits - 1));
 154   dinfo->EOFCode = dinfo->ClearCode + 1;
 155   dinfo->code_counter = dinfo->ClearCode + 2;
 156   /* init output buffering vars */
 157   dinfo->bytesinpkt = 0;
 158   dinfo->cur_accum = 0;
 159   dinfo->cur_bits = 0;
 160   /* GIF specifies an initial Clear code */
 161   output(dinfo, dinfo->ClearCode);
 162 }
 163
 164
 165 LOCAL(void)
 166 compress_pixel (gif_dest_ptr dinfo, int c)
 167 /* Accept and "compress" one pixel value.
 168  * The given value must be less than n_bits wide.
 169  */
 170 {
 171   /* Output the given pixel value as a symbol. */
 172   output(dinfo, c);
 173   /* Issue Clear codes often enough to keep the reader from ratcheting up
 174    * its symbol size.
 175    */
 176   if (dinfo->code_counter < dinfo->maxcode) {
 177     dinfo->code_counter++;
 178   } else {
 179     output(dinfo, dinfo->ClearCode);
 180     dinfo->code_counter = dinfo->ClearCode + 2; /* reset the counter */
 181   }
 182 }
 183
 184
 185 LOCAL(void)
 186 compress_term (gif_dest_ptr dinfo)
 187 /* Clean up at end */
 188 {
 189   /* Send an EOF code */
 190   output(dinfo, dinfo->EOFCode);
 191   /* Flush the bit-packing buffer */
 192   if (dinfo->cur_bits > 0) {
 193     CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF);
 194   }
 195   /* Flush the packet buffer */
 196   flush_packet(dinfo);
 197 }
 198
 199
 200 /* GIF header construction */
 201
 202
 203 LOCAL(void)
 204 put_word (gif_dest_ptr dinfo, unsigned int w)
 205 /* Emit a 16-bit word, LSB first */
 206 {
 207   putc(w & 0xFF, dinfo->pub.output_file);
 208   putc((w >> 8) & 0xFF, dinfo->pub.output_file);
 209 }
 210
 211
 212 LOCAL(void)
 213 put_3bytes (gif_dest_ptr dinfo, int val)
 214 /* Emit 3 copies of same byte value --- handy subr for colormap construction */
 215 {
 216   putc(val, dinfo->pub.output_file);
 217   putc(val, dinfo->pub.output_file);
 218   putc(val, dinfo->pub.output_file);
 219 }
 220
 221
 222 LOCAL(void)
 223 emit_header (gif_dest_ptr dinfo, int num_colors, JSAMPARRAY colormap)
 224 /* Output the GIF file header, including color map */
 225 /* If colormap==NULL, synthesize a gray-scale colormap */
 226 {
 227   int BitsPerPixel, ColorMapSize, InitCodeSize, FlagByte;
 228   int cshift = dinfo->cinfo->data_precision - 8;
 229   int i;
 230
 231   if (num_colors > 256)
 232     ERREXIT1(dinfo->cinfo, JERR_TOO_MANY_COLORS, num_colors);
 233   /* Compute bits/pixel and related values */
 234   BitsPerPixel = 1;
 235   while (num_colors > (1 << BitsPerPixel))
 236     BitsPerPixel++;
 237   ColorMapSize = 1 << BitsPerPixel;
 238   if (BitsPerPixel <= 1)
 239     InitCodeSize = 2;
 240   else
 241     InitCodeSize = BitsPerPixel;
 242   /*
 243    * Write the GIF header.
 244    * Note that we generate a plain GIF87 header for maximum compatibility.
 245    */
 246   putc('G', dinfo->pub.output_file);
 247   putc('I', dinfo->pub.output_file);
 248   putc('F', dinfo->pub.output_file);
 249   putc('8', dinfo->pub.output_file);
 250   putc('7', dinfo->pub.output_file);
 251   putc('a', dinfo->pub.output_file);
 252   /* Write the Logical Screen Descriptor */
 253   put_word(dinfo, (unsigned int) dinfo->cinfo->output_width);
 254   put_word(dinfo, (unsigned int) dinfo->cinfo->output_height);
 255   FlagByte = 0x80;              /* Yes, there is a global color table */
 256   FlagByte |= (BitsPerPixel-1) << 4; /* color resolution */
 257   FlagByte |= (BitsPerPixel-1); /* size of global color table */
 258   putc(FlagByte, dinfo->pub.output_file);
 259   putc(0, dinfo->pub.output_file); /* Background color index */
 260   putc(0, dinfo->pub.output_file); /* Reserved (aspect ratio in GIF89) */
 261   /* Write the Global Color Map */
 262   /* If the color map is more than 8 bits precision, */
 263   /* we reduce it to 8 bits by shifting */
 264   for (i=0; i < ColorMapSize; i++) {
 265     if (i < num_colors) {
 266       if (colormap != NULL) {
 267         if (dinfo->cinfo->out_color_space == JCS_RGB) {
 268           /* Normal case: RGB color map */
 269           putc(GETJSAMPLE(colormap[0][i]) >> cshift, dinfo->pub.output_file);
 270           putc(GETJSAMPLE(colormap[1][i]) >> cshift, dinfo->pub.output_file);
 271           putc(GETJSAMPLE(colormap[2][i]) >> cshift, dinfo->pub.output_file);
 272         } else {
 273           /* Grayscale "color map": possible if quantizing grayscale image */
 274           put_3bytes(dinfo, GETJSAMPLE(colormap[0][i]) >> cshift);
 275         }
 276       } else {
 277         /* Create a gray-scale map of num_colors values, range 0..255 */
 278         put_3bytes(dinfo, (i * 255 + (num_colors-1)/2) / (num_colors-1));
 279       }
 280     } else {
 281       /* fill out the map to a power of 2 */
 282       put_3bytes(dinfo, 0);
 283     }
 284   }
 285   /* Write image separator and Image Descriptor */
 286   putc(',', dinfo->pub.output_file); /* separator */
 287   put_word(dinfo, 0);           /* left/top offset */
 288   put_word(dinfo, 0);
 289   put_word(dinfo, (unsigned int) dinfo->cinfo->output_width); /* image size */
 290   put_word(dinfo, (unsigned int) dinfo->cinfo->output_height);
 291   /* flag byte: not interlaced, no local color map */
 292   putc(0x00, dinfo->pub.output_file);
 293   /* Write Initial Code Size byte */
 294   putc(InitCodeSize, dinfo->pub.output_file);
 295
 296   /* Initialize for "compression" of image data */
 297   compress_init(dinfo, InitCodeSize+1);
 298 }
 299
 300
 301 /*
 302  * Startup: write the file header.
 303  */
 304
 305 METHODDEF(void)
 306 start_output_gif (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
 307 {
 308   gif_dest_ptr dest = (gif_dest_ptr) dinfo;
 309
 310   if (cinfo->quantize_colors)
 311     emit_header(dest, cinfo->actual_number_of_colors, cinfo->colormap);
 312   else
 313     emit_header(dest, 256, (JSAMPARRAY) NULL);
 314 }
 315
 316
 317 /*
 318  * Write some pixel data.
 319  * In this module rows_supplied will always be 1.
 320  */
 321
 322 METHODDEF(void)
 323 put_pixel_rows (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo,
 324                 JDIMENSION rows_supplied)
 325 {
 326   gif_dest_ptr dest = (gif_dest_ptr) dinfo;
 327   register JSAMPROW ptr;
 328   register JDIMENSION col;
 329
 330   ptr = dest->pub.buffer[0];
 331   for (col = cinfo->output_width; col > 0; col--) {
 332     compress_pixel(dest, GETJSAMPLE(*ptr++));
 333   }
 334 }
 335
 336
 337 /*
 338  * Finish up at the end of the file.
 339  */
 340
 341 METHODDEF(void)
 342 finish_output_gif (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
 343 {
 344   gif_dest_ptr dest = (gif_dest_ptr) dinfo;
 345
 346   /* Flush "compression" mechanism */
 347   compress_term(dest);
 348   /* Write a zero-length data block to end the series */
 349   putc(0, dest->pub.output_file);
 350   /* Write the GIF terminator mark */
 351   putc(';', dest->pub.output_file);
 352   /* Make sure we wrote the output file OK */
 353   fflush(dest->pub.output_file);
 354   if (ferror(dest->pub.output_file))
 355     ERREXIT(cinfo, JERR_FILE_WRITE);
 356 }
 357
 358
 359 /*
 360  * The module selection routine for GIF format output.
 361  */
 362
 363 JGLOBAL(djpeg_dest_ptr)
 364 jinit_write_gif (j_decompress_ptr cinfo)
 365 {
 366   gif_dest_ptr dest;
 367
 368   /* Create module interface object, fill in method pointers */
 369   dest = (gif_dest_ptr)
 370       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 371                                   SIZEOF(gif_dest_struct));
 372   dest->cinfo = cinfo;          /* make back link for subroutines */
 373   dest->pub.start_output = start_output_gif;
 374   dest->pub.put_pixel_rows = put_pixel_rows;
 375   dest->pub.finish_output = finish_output_gif;
 376
 377   if (cinfo->out_color_space != JCS_GRAYSCALE &&
 378       cinfo->out_color_space != JCS_RGB)
 379     ERREXIT(cinfo, JERR_GIF_COLORSPACE);
 380
 381   /* Force quantization if color or if > 8 bits input */
 382   if (cinfo->out_color_space != JCS_GRAYSCALE || cinfo->data_precision > 8) {
 383     /* Force quantization to at most 256 colors */
 384     cinfo->quantize_colors = TRUE;
 385     if (cinfo->desired_number_of_colors > 256)
 386       cinfo->desired_number_of_colors = 256;
 387   }
 388
 389   /* Calculate output image dimensions so we can allocate space */
 390   jpeg_calc_output_dimensions(cinfo);
 391
 392   if (cinfo->output_components != 1) /* safety check: just one component? */
 393     ERREXIT(cinfo, JERR_GIF_BUG);
 394
 395   /* Create decompressor output buffer. */
 396   dest->pub.buffer = (*cinfo->mem->alloc_sarray)
 397     ((j_common_ptr) cinfo, JPOOL_IMAGE, cinfo->output_width, (JDIMENSION) 1);
 398   dest->pub.buffer_height = 1;
 399
 400   return (djpeg_dest_ptr) dest;
 401 }
 402
 403 #endif /* GIF_SUPPORTED */