workbench/libs/png/contrib/examples/pngtopng.c

   1 /*- pngtopng
   2  *
   3  * COPYRIGHT: Written by John Cunningham Bowler, 2011, 2017.
   4  * To the extent possible under law, the author has waived all copyright and
   5  * related or neighboring rights to this work.  This work is published from:
   6  * United States.
   7  *
   8  * Last changed in libpng 1.6.29 [March 16, 2017]
   9  *
  10  * Read a PNG and write it out in a fixed format, using the 'simplified API'
  11  * that was introduced in libpng-1.6.0.
  12  *
  13  * This sample code is just the code from the top of 'example.c' with some error
  14  * handling added.  See example.c for more comments.
  15  */
  16 #include <stddef.h>
  17 #include <stdlib.h>
  18 #include <string.h>
  19 #include <stdio.h>
  20
  21 /* Normally use <png.h> here to get the installed libpng, but this is done to
  22  * ensure the code picks up the local libpng implementation:
  23  */
  24 #include "../../png.h"
  25 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && \
  26     defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
  27
  28 int main(int argc, const char **argv)
  29 {
  30    int result = 1;
  31
  32    if (argc == 3)
  33    {
  34       png_image image;
  35
  36       /* Only the image structure version number needs to be set. */
  37       memset(&image, 0, sizeof image);
  38       image.version = PNG_IMAGE_VERSION;
  39
  40       if (png_image_begin_read_from_file(&image, argv[1]))
  41       {
  42          png_bytep buffer;
  43
  44          /* Change this to try different formats!  If you set a colormap format
  45           * then you must also supply a colormap below.
  46           */
  47          image.format = PNG_FORMAT_RGBA;
  48
  49          buffer = malloc(PNG_IMAGE_SIZE(image));
  50
  51          if (buffer != NULL)
  52          {
  53             if (png_image_finish_read(&image, NULL/*background*/, buffer,
  54                0/*row_stride*/, NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP */))
  55             {
  56                if (png_image_write_to_file(&image, argv[2],
  57                   0/*convert_to_8bit*/, buffer, 0/*row_stride*/,
  58                   NULL/*colormap*/))
  59                   result = 0;
  60
  61                else
  62                   fprintf(stderr, "pngtopng: write %s: %s\n", argv[2],
  63                       image.message);
  64             }
  65
  66             else
  67                fprintf(stderr, "pngtopng: read %s: %s\n", argv[1],
  68                    image.message);
  69
  70             free(buffer);
  71          }
  72
  73          else
  74          {
  75             fprintf(stderr, "pngtopng: out of memory: %lu bytes\n",
  76                (unsigned long)PNG_IMAGE_SIZE(image));
  77
  78             /* This is the only place where a 'free' is required; libpng does
  79              * the cleanup on error and success, but in this case we couldn't
  80              * complete the read because of running out of memory and so libpng
  81              * has not got to the point where it can do cleanup.
  82              */
  83             png_image_free(&image);
  84          }
  85       }
  86
  87       else
  88          /* Failed to read the first argument: */
  89          fprintf(stderr, "pngtopng: %s: %s\n", argv[1], image.message);
  90    }
  91
  92    else
  93       /* Wrong number of arguments */
  94       fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n");
  95
  96    return result;
  97 }
  98 #endif /* READ && WRITE */