(imagemagick_compute_animated_image): Respect the GIF disposal methods.

2 files changed, 19 insertions, 3 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index c12b32ebc71..028c33848a4 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2013-08-15  Lars Magne Ingebrigtsen  <larsi@gnus.org>
+
+        * image.c (imagemagick_compute_animated_image): Respect the GIF
+        disposal methods.
+
 2013-08-15  Ken Brown  <kbrown@cornell.edu>
 
         * emacs.c (main): Update comment about G_SLICE_ALWAYS_MALLOC.
diff --git a/src/image.c b/src/image.c
index 3cab72edf74..3c5ee4ce66f 100644
--- a/src/image.c
+++ b/src/image.c
@@ -7887,17 +7887,20 @@ imagemagick_compute_animated_image (MagickWand *super_wand, int ino)
   else
     composite_wand = animation_cache;
 
-  for (i = max (1, animation_index); i <= ino; i++)
+  for (i = max (1, animation_index + 1); i <= ino; i++)
     {
       MagickWand *sub_wand;
       PixelIterator *source_iterator, *dest_iterator;
       PixelWand **source, **dest;
       size_t source_width, dest_width;
       MagickPixelPacket pixel;
+      DisposeType dispose;
 
       MagickSetIteratorIndex (super_wand, i);
       sub_wand = MagickGetImage (super_wand);
 
+      dispose = MagickGetImageDispose (sub_wand);
+
       source_iterator = NewPixelIterator (sub_wand);
       if (! source_iterator)
         {
@@ -7926,12 +7929,20 @@ imagemagick_compute_animated_image (MagickWand *super_wand, int ino)
           dest = PixelGetNextIteratorRow (dest_iterator, &dest_width);
           for (x = 0; x < source_width; x++)
             {
-              /* Copy over non-transparent pixels. */
-              if (PixelGetAlpha (source[x]))
+              if (dispose == BackgroundDispose)
                 {
                   PixelGetMagickColor (source[x], &pixel);
                   PixelSetMagickColor (dest[x], &pixel);
                 }
+              else
+                {
+                  /* Copy over non-transparent pixels. */
+                  if (PixelGetAlpha (source[x]))
+                    {
+                      PixelGetMagickColor (source[x], &pixel);
+                      PixelSetMagickColor (dest[x], &pixel);
+                    }
+                }
             }
           PixelSyncIterator(dest_iterator);
         }