external/io_grib2/g2lib/dec_png.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4 #include <png.h>
   5 #include "proto.h"
   6
   7 #ifdef __64BIT__
   8   typedef int g2int;
   9 #else
  10   typedef long g2int;
  11 #endif
  12
  13 struct png_stream {
  14    unsigned char *stream_ptr;     /*  location to write PNG stream  */
  15    g2int stream_len;               /*  number of bytes written       */
  16 };
  17 typedef struct png_stream png_stream;
  18
  19 void user_read_data(png_structp , png_bytep , png_uint_32 );
  20
  21 void user_read_data(png_structp png_ptr,png_bytep data, png_uint_32 length)
  22 /*
  23         Custom read function used so that libpng will read a PNG stream
  24         from memory instead of a file on disk.
  25 */
  26 {
  27      char *ptr;
  28      g2int offset;
  29      png_stream *mem;
  30
  31      mem=(png_stream *)png_get_io_ptr(png_ptr);
  32      ptr=(void *)mem->stream_ptr;
  33      offset=mem->stream_len;
  34 /*     printf("SAGrd %ld %ld %x\n",offset,length,ptr);  */
  35      memcpy(data,ptr+offset,length);
  36      mem->stream_len += length;
  37 }
  38
  39
  40
  41 int DEC_PNG(unsigned char *pngbuf,g2int *width,g2int *height,char *cout)
  42 {
  43     int interlace,color,compres,filter,bit_depth;
  44     g2int j,k,n,bytes,clen;
  45     png_structp png_ptr;
  46     png_infop info_ptr,end_info;
  47     png_bytepp row_pointers;
  48     png_stream read_io_ptr;
  49
  50 /*  check if stream is a valid PNG format   */
  51
  52     if ( png_sig_cmp(pngbuf,0,8) != 0)
  53        return (-3);
  54
  55 /* create and initialize png_structs  */
  56
  57     png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, (png_voidp)NULL,
  58                                       NULL, NULL);
  59     if (!png_ptr)
  60        return (-1);
  61
  62     info_ptr = png_create_info_struct(png_ptr);
  63     if (!info_ptr)
  64     {
  65        png_destroy_read_struct(&png_ptr,(png_infopp)NULL,(png_infopp)NULL);
  66        return (-2);
  67     }
  68
  69     end_info = png_create_info_struct(png_ptr);
  70     if (!end_info)
  71     {
  72        png_destroy_read_struct(&png_ptr,(png_infopp)info_ptr,(png_infopp)NULL);
  73        return (-2);
  74     }
  75
  76 /*     Set Error callback   */
  77
  78     if (setjmp(png_jmpbuf(png_ptr)))
  79     {
  80        png_destroy_read_struct(&png_ptr, &info_ptr,&end_info);
  81        return (-3);
  82     }
  83
  84 /*    Initialize info for reading PNG stream from memory   */
  85
  86     read_io_ptr.stream_ptr=(png_voidp)pngbuf;
  87     read_io_ptr.stream_len=0;
  88
  89 /*    Set new custom read function    */
  90
  91     png_set_read_fn(png_ptr,(png_voidp)&read_io_ptr,(png_rw_ptr)user_read_data);
  92 /*     png_init_io(png_ptr, fptr);   */
  93
  94 /*     Read and decode PNG stream   */
  95
  96     png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
  97
  98 /*     Get pointer to each row of image data   */
  99
 100     row_pointers = png_get_rows(png_ptr, info_ptr);
 101
 102 /*     Get image info, such as size, depth, colortype, etc...   */
 103
 104     /*printf("SAGT:png %d %d %d\n",info_ptr->width,info_ptr->height,info_ptr->bit_depth);*/
 105     (void)png_get_IHDR(png_ptr, info_ptr, (png_uint_32 *)width, (png_uint_32 *)height,
 106                &bit_depth, &color, &interlace, &compres, &filter);
 107
 108 /*     Check if image was grayscale      */
 109
 110 /*
 111     if (color != PNG_COLOR_TYPE_GRAY ) {
 112        fprintf(stderr,"dec_png: Grayscale image was expected. \n");
 113     }
 114 */
 115     if ( color == PNG_COLOR_TYPE_RGB ) {
 116        bit_depth=24;
 117     }
 118     else if ( color == PNG_COLOR_TYPE_RGB_ALPHA ) {
 119        bit_depth=32;
 120     }
 121 /*     Copy image data to output string   */
 122
 123     n=0;
 124     bytes=bit_depth/8;
 125     clen=(*width)*bytes;
 126     for (j=0;j<*height;j++) {
 127       for (k=0;k<clen;k++) {
 128         cout[n]=*(row_pointers[j]+k);
 129         n++;
 130       }
 131     }
 132
 133 /*      Clean up   */
 134
 135     png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
 136     return 0;
 137
 138 }
 139