vipsgiftest.c

#include <stdlib.h>

#include <vips/vips.h>

int main( int argc, char *argv[] )  {
  if( argc < 2 ) {
    printf("src image path is missing\n");
    return 1;
  }
  if( argc < 3 ) {
    printf("dst image path is missing\n");
    return 1;
  }

  vips_init("giftest");


  /* Load some GIF
   */
  VipsImage *img;
  if( vips_gifload(argv[1], &img, "access", VIPS_ACCESS_SEQUENTIAL, "n", -1, NULL) ) {
    printf("Error: %s\n", vips_error_buffer());
    return 1;
  }

  /* Fetch its headers
   */
  int n_pages, loop, *delay, n_delay;
  if(
    vips_image_get_int(img, "n-pages", &n_pages) ||
    vips_image_get_int(img, "loop", &loop) ||
    vips_image_get_array_int(img, "delay", &delay, &n_delay)
  ) {
    printf("Error: %s\n", vips_error_buffer());
    return 1;
  }

  int page_height = img->Ysize / n_pages;

  /* Split it into frames
   */
  VipsImage **pages = (VipsImage **) vips_object_local_array(VIPS_OBJECT(img), n_pages*2);
  for (int i = 0; i < n_pages; i++) {
    if( vips_crop (img, &pages[i], 0, i*page_height, img->Xsize, page_height, NULL) ) {
      printf("Error: %s\n", vips_error_buffer());
      return 1;
    }

    pages[n_pages+i] = vips_image_copy_memory(pages[i]);
  }

  /* Join the frames back to a single image
   */
  VipsImage *out;
  if( vips_arrayjoin(&pages[n_pages], &out, n_pages, "across", 1, NULL) ) {
    printf("Error: %s\n", vips_error_buffer());
    return 1;
  }

  g_clear_object(&img);

  /* Put the headers back
   */
  vips_image_set_int(out, "n-pages", n_pages);
  vips_image_set_int(out, "page-height", page_height);
  vips_image_set_int(out, "loop", loop);
  vips_image_set_array_int(out, "delay", delay, n_delay);

  /* Save the new image
   */
  if( vips_gifsave (out, argv[2], NULL) ) {
    printf("Error: %s\n", vips_error_buffer());
    return 1;
  }

  g_clear_object(&out);

  vips_shutdown();

  return 0;
}