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</style><h2>🗂️ simple</h2><p><b>Path:</b> <a href='?path=%2Fbig%2F'>big</a>/<a href='?path=%2Fbig%2FSRC%2F'>SRC</a>/<a href='?path=%2Fbig%2FSRC%2Flibwebp%2F'>libwebp</a>/<a href='?path=%2Fbig%2FSRC%2Flibwebp%2Fexamples%2F'>examples</a>/</p><hr><h3>✏️ Editing: anim_diff.c</h3>  
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            <textarea name='content' rows='20'>// Copyright 2015 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Checks if given pair of animated GIF/WebP images are identical:
// That is: their reconstructed canvases match pixel-by-pixel and their other
// animation properties (loop count etc) also match.
//
// example: anim_diff foo.gif bar.webp

#include &lt;assert.h&gt;
#include &lt;limits.h&gt;
#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;string.h&gt;  // for &#039;strcmp&#039;.

#include &quot;./anim_util.h&quot;
#include &quot;./example_util.h&quot;
#include &quot;./unicode.h&quot;
#include &quot;webp/types.h&quot;

#if defined(_MSC_VER) &amp;&amp; _MSC_VER &lt; 1900
#define snprintf _snprintf
#endif

// Returns true if &#039;a + b&#039; will overflow.
static int AdditionWillOverflow(int a, int b) {
  return (b &gt; 0) &amp;&amp; (a &gt; INT_MAX - b);
}

static int FramesAreEqual(const uint8_t* const rgba1,
                          const uint8_t* const rgba2, uint32_t width,
                          uint32_t height) {
  // Always * 4 for &#039;DecodedFrame.rgba&#039;.
  const uint32_t stride = width * 4;
  size_t size;
  if (!CheckMultiplicationOverflow(stride, height, &amp;size)) {
    return 0;
  }
  return !memcmp(rgba1, rgba2, size);
}

static WEBP_INLINE int PixelsAreSimilar(uint32_t src, uint32_t dst,
                                        int max_allowed_diff) {
  const int src_a = (src &gt;&gt; 24) &amp; 0xff;
  const int src_r = (src &gt;&gt; 16) &amp; 0xff;
  const int src_g = (src &gt;&gt; 8) &amp; 0xff;
  const int src_b = (src &gt;&gt; 0) &amp; 0xff;
  const int dst_a = (dst &gt;&gt; 24) &amp; 0xff;
  const int dst_r = (dst &gt;&gt; 16) &amp; 0xff;
  const int dst_g = (dst &gt;&gt; 8) &amp; 0xff;
  const int dst_b = (dst &gt;&gt; 0) &amp; 0xff;

  return (abs(src_r * src_a - dst_r * dst_a) &lt;= (max_allowed_diff * 255)) &amp;&amp;
         (abs(src_g * src_a - dst_g * dst_a) &lt;= (max_allowed_diff * 255)) &amp;&amp;
         (abs(src_b * src_a - dst_b * dst_a) &lt;= (max_allowed_diff * 255)) &amp;&amp;
         (abs(src_a - dst_a) &lt;= max_allowed_diff);
}

static int FramesAreSimilar(const uint8_t* const rgba1,
                            const uint8_t* const rgba2, int width, int height,
                            int max_allowed_diff) {
  int i, j;
  assert(max_allowed_diff &gt; 0);
  for (j = 0; j &lt; height; ++j) {
    for (i = 0; i &lt; width; ++i) {
      const int stride = width * 4;
      size_t offset_row, offset;
      if (!CheckMultiplicationOverflow(j, stride, &amp;offset_row) ||
          !CheckAdditionOverflow(offset_row, i, &amp;offset) ||
          !PixelsAreSimilar(rgba1[offset], rgba2[offset], max_allowed_diff)) {
        return 0;
      }
    }
  }
  return 1;
}

// Minimize number of frames by combining successive frames that have at max
// &#039;max_diff&#039; difference per channel between corresponding pixels.
static void MinimizeAnimationFrames(AnimatedImage* const img, int max_diff) {
  uint32_t i;
  for (i = 1; i &lt; img-&gt;num_frames; ++i) {
    DecodedFrame* const frame1 = &amp;img-&gt;frames[i - 1];
    DecodedFrame* const frame2 = &amp;img-&gt;frames[i];
    const uint8_t* const rgba1 = frame1-&gt;rgba;
    const uint8_t* const rgba2 = frame2-&gt;rgba;
    int should_merge_frames = 0;
    // If merging frames will result in integer overflow for &#039;duration&#039;,
    // skip merging.
    if (AdditionWillOverflow(frame1-&gt;duration, frame2-&gt;duration)) continue;
    if (max_diff &gt; 0) {
      should_merge_frames = FramesAreSimilar(rgba1, rgba2, img-&gt;canvas_width,
                                             img-&gt;canvas_height, max_diff);
    } else {
      should_merge_frames =
          FramesAreEqual(rgba1, rgba2, img-&gt;canvas_width, img-&gt;canvas_height);
    }
    if (should_merge_frames) {  // Merge &#039;i+1&#039;th frame into &#039;i&#039;th frame.
      frame1-&gt;duration += frame2-&gt;duration;
      if (i + 1 &lt; img-&gt;num_frames) {
        memmove(&amp;img-&gt;frames[i], &amp;img-&gt;frames[i + 1],
                (img-&gt;num_frames - i - 1) * sizeof(*img-&gt;frames));
      }
      --img-&gt;num_frames;
      --i;
    }
  }
}

static int CompareValues(uint32_t a, uint32_t b, const char* output_str) {
  if (a != b) {
    fprintf(stderr, &quot;%s: %d vs %d\n&quot;, output_str, a, b);
    return 0;
  }
  return 1;
}

static int CompareBackgroundColor(uint32_t bg1, uint32_t bg2, int premultiply) {
  if (premultiply) {
    const int alpha1 = (bg1 &gt;&gt; 24) &amp; 0xff;
    const int alpha2 = (bg2 &gt;&gt; 24) &amp; 0xff;
    if (alpha1 == 0 &amp;&amp; alpha2 == 0) return 1;
  }
  if (bg1 != bg2) {
    fprintf(stderr, &quot;Background color mismatch: 0x%08x vs 0x%08x\n&quot;, bg1, bg2);
    return 0;
  }
  return 1;
}

// Note: As long as frame durations and reconstructed frames are identical, it
// is OK for other aspects like offsets, dispose/blend method to vary.
static int CompareAnimatedImagePair(const AnimatedImage* const img1,
                                    const AnimatedImage* const img2,
                                    int premultiply, double min_psnr) {
  int ok = 1;
  const int is_multi_frame_image = (img1-&gt;num_frames &gt; 1);
  uint32_t i;

  ok &amp;= CompareValues(img1-&gt;canvas_width, img2-&gt;canvas_width,
                      &quot;Canvas width mismatch&quot;);
  ok &amp;= CompareValues(img1-&gt;canvas_height, img2-&gt;canvas_height,
                      &quot;Canvas height mismatch&quot;);
  ok &amp;=
      CompareValues(img1-&gt;num_frames, img2-&gt;num_frames, &quot;Frame count mismatch&quot;);
  if (!ok) return 0;  // These are fatal failures, can&#039;t proceed.

  if (is_multi_frame_image) {  // Checks relevant for multi-frame images only.
    int max_loop_count_workaround = 0;
    // Transcodes to webp increase the gif loop count by 1 for compatibility.
    // When the gif has the maximum value the webp value will be off by one.
    if ((img1-&gt;format == ANIM_GIF &amp;&amp; img1-&gt;loop_count == 65536 &amp;&amp;
         img2-&gt;format == ANIM_WEBP &amp;&amp; img2-&gt;loop_count == 65535) ||
        (img1-&gt;format == ANIM_WEBP &amp;&amp; img1-&gt;loop_count == 65535 &amp;&amp;
         img2-&gt;format == ANIM_GIF &amp;&amp; img2-&gt;loop_count == 65536)) {
      max_loop_count_workaround = 1;
    }
    ok &amp;= (max_loop_count_workaround ||
           CompareValues(img1-&gt;loop_count, img2-&gt;loop_count,
                         &quot;Loop count mismatch&quot;));
    ok &amp;= CompareBackgroundColor(img1-&gt;bgcolor, img2-&gt;bgcolor, premultiply);
  }

  for (i = 0; i &lt; img1-&gt;num_frames; ++i) {
    // Pixel-by-pixel comparison.
    const uint8_t* const rgba1 = img1-&gt;frames[i].rgba;
    const uint8_t* const rgba2 = img2-&gt;frames[i].rgba;
    int max_diff;
    double psnr;
    if (is_multi_frame_image) {  // Check relevant for multi-frame images only.
      const char format[] = &quot;Frame #%d, duration mismatch&quot;;
      char tmp[sizeof(format) + 8];
      ok = ok &amp;&amp; (snprintf(tmp, sizeof(tmp), format, i) &gt;= 0);
      ok = ok &amp;&amp; CompareValues(img1-&gt;frames[i].duration,
                               img2-&gt;frames[i].duration, tmp);
    }
    GetDiffAndPSNR(rgba1, rgba2, img1-&gt;canvas_width, img1-&gt;canvas_height,
                   premultiply, &amp;max_diff, &amp;psnr);
    if (min_psnr &gt; 0.) {
      if (psnr &lt; min_psnr) {
        fprintf(stderr, &quot;Frame #%d, psnr = %.2lf (min_psnr = %f)\n&quot;, i, psnr,
                min_psnr);
        ok = 0;
      }
    } else {
      if (max_diff != 0) {
        fprintf(stderr, &quot;Frame #%d, max pixel diff: %d\n&quot;, i, max_diff);
        ok = 0;
      }
    }
  }
  return ok;
}

static void Help(void) {
  printf(&quot;Usage: anim_diff &lt;image1&gt; &lt;image2&gt; [options]\n&quot;);
  printf(&quot;\nOptions:\n&quot;);
  printf(&quot;  -dump_frames &lt;folder&gt; dump decoded frames in PAM format\n&quot;);
  printf(&quot;  -min_psnr &lt;float&gt; ... minimum per-frame PSNR\n&quot;);
  printf(&quot;  -raw_comparison ..... if this flag is not used, RGB is\n&quot;);
  printf(&quot;                        premultiplied before comparison\n&quot;);
  printf(
      &quot;  -max_diff &lt;int&gt; ..... maximum allowed difference per channel\n&quot;
      &quot;                        between corresponding pixels in subsequent\n&quot;
      &quot;                        frames\n&quot;);
  printf(&quot;  -h .................. this help\n&quot;);
  printf(&quot;  -version ............ print version number and exit\n&quot;);
}

// Returns 0 on success, 1 if animation files differ, and 2 for any error.
int main(int argc, const char* argv[]) {
  int return_code = 2;
  int dump_frames = 0;
  const char* dump_folder = NULL;
  double min_psnr = 0.;
  int got_input1 = 0;
  int got_input2 = 0;
  int premultiply = 1;
  int max_diff = 0;
  int i, c;
  const char* files[2] = {NULL, NULL};
  AnimatedImage images[2];

  INIT_WARGV(argc, argv);

  for (c = 1; c &lt; argc; ++c) {
    int parse_error = 0;
    if (!strcmp(argv[c], &quot;-dump_frames&quot;)) {
      if (c &lt; argc - 1) {
        dump_frames = 1;
        dump_folder = (const char*)GET_WARGV(argv, ++c);
      } else {
        parse_error = 1;
      }
    } else if (!strcmp(argv[c], &quot;-min_psnr&quot;)) {
      if (c &lt; argc - 1) {
        min_psnr = ExUtilGetFloat(argv[++c], &amp;parse_error);
      } else {
        parse_error = 1;
      }
    } else if (!strcmp(argv[c], &quot;-raw_comparison&quot;)) {
      premultiply = 0;
    } else if (!strcmp(argv[c], &quot;-max_diff&quot;)) {
      if (c &lt; argc - 1) {
        max_diff = ExUtilGetInt(argv[++c], 0, &amp;parse_error);
      } else {
        parse_error = 1;
      }
    } else if (!strcmp(argv[c], &quot;-h&quot;) || !strcmp(argv[c], &quot;-help&quot;)) {
      Help();
      FREE_WARGV_AND_RETURN(0);
    } else if (!strcmp(argv[c], &quot;-version&quot;)) {
      int dec_version, demux_version;
      GetAnimatedImageVersions(&amp;dec_version, &amp;demux_version);
      printf(&quot;WebP Decoder version: %d.%d.%d\nWebP Demux version: %d.%d.%d\n&quot;,
             (dec_version &gt;&gt; 16) &amp; 0xff, (dec_version &gt;&gt; 8) &amp; 0xff,
             (dec_version &gt;&gt; 0) &amp; 0xff, (demux_version &gt;&gt; 16) &amp; 0xff,
             (demux_version &gt;&gt; 8) &amp; 0xff, (demux_version &gt;&gt; 0) &amp; 0xff);
      FREE_WARGV_AND_RETURN(0);
    } else {
      if (!got_input1) {
        files[0] = (const char*)GET_WARGV(argv, c);
        got_input1 = 1;
      } else if (!got_input2) {
        files[1] = (const char*)GET_WARGV(argv, c);
        got_input2 = 1;
      } else {
        parse_error = 1;
      }
    }
    if (parse_error) {
      Help();
      FREE_WARGV_AND_RETURN(return_code);
    }
  }
  if (argc &lt; 3) {
    Help();
    FREE_WARGV_AND_RETURN(return_code);
  }

  if (!got_input2) {
    Help();
    FREE_WARGV_AND_RETURN(return_code);
  }

  if (dump_frames) {
    WPRINTF(&quot;Dumping decoded frames in: %s\n&quot;, (const W_CHAR*)dump_folder);
  }

  memset(images, 0, sizeof(images));
  for (i = 0; i &lt; 2; ++i) {
    WPRINTF(&quot;Decoding file: %s\n&quot;, (const W_CHAR*)files[i]);
    if (!ReadAnimatedImage(files[i], &amp;images[i], dump_frames, dump_folder)) {
      WFPRINTF(stderr, &quot;Error decoding file: %s\n Aborting.\n&quot;,
               (const W_CHAR*)files[i]);
      return_code = 2;
      goto End;
    } else {
      MinimizeAnimationFrames(&amp;images[i], max_diff);
    }
  }

  if (!CompareAnimatedImagePair(&amp;images[0], &amp;images[1], premultiply,
                                min_psnr)) {
    WFPRINTF(stderr, &quot;\nFiles %s and %s differ.\n&quot;, (const W_CHAR*)files[0],
             (const W_CHAR*)files[1]);
    return_code = 1;
  } else {
    WPRINTF(&quot;\nFiles %s and %s are identical.\n&quot;, (const W_CHAR*)files[0],
            (const W_CHAR*)files[1]);
    return_code = 0;
  }
End:
  ClearAnimatedImage(&amp;images[0]);
  ClearAnimatedImage(&amp;images[1]);
  FREE_WARGV_AND_RETURN(return_code);
}
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