image.c animation touchups

* image.c (imagemagick_compute_animated_image): Animate correctly
when sub-images are smaller than the main image.

1 files changed, 31 insertions, 2 deletions

diff --git a/src/image.c b/src/image.c
index bc9f9ab123a..348f6a8209b 100644
--- a/src/image.c
+++ b/src/image.c
@@ -7879,6 +7879,7 @@ imagemagick_compute_animated_image (MagickWand *super_wand, int ino)
 {
   int i;
   MagickWand *composite_wand;
+  size_t dest_width, dest_height;
 
   MagickSetIteratorIndex (super_wand, 0);
 
@@ -7887,18 +7888,36 @@ imagemagick_compute_animated_image (MagickWand *super_wand, int ino)
   else
     composite_wand = animation_cache;
 
+  dest_width = MagickGetImageWidth (composite_wand);
+  dest_height = MagickGetImageHeight (composite_wand);
+
   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;
+      size_t source_width, source_height;
+      ssize_t source_left, source_top;
       MagickPixelPacket pixel;
       DisposeType dispose;
 
       MagickSetIteratorIndex (super_wand, i);
       sub_wand = MagickGetImage (super_wand);
 
+      MagickGetImagePage (sub_wand, &source_width, &source_height,
+                          &source_left, &source_top);
+
+      /* Sanity check.  The sub-image should not be bigger than the
+         base image.  */
+      if (source_height + source_top > dest_height)
+        {
+          DestroyMagickWand (composite_wand);
+          DestroyMagickWand (sub_wand);
+          animation_cache = NULL;
+          image_error ("Inconsinstent animation size", Qnil, Qnil);
+          return NULL;
+        }
+
       dispose = MagickGetImageDispose (sub_wand);
 
       source_iterator = NewPixelIterator (sub_wand);
@@ -7906,6 +7925,7 @@ imagemagick_compute_animated_image (MagickWand *super_wand, int ino)
         {
           DestroyMagickWand (composite_wand);
           DestroyMagickWand (sub_wand);
+          animation_cache = NULL;
           image_error ("Imagemagick pixel iterator creation failed",
                        Qnil, Qnil);
           return NULL;
@@ -7917,11 +7937,16 @@ imagemagick_compute_animated_image (MagickWand *super_wand, int ino)
           DestroyMagickWand (composite_wand);
           DestroyMagickWand (sub_wand);
           DestroyPixelIterator (source_iterator);
+          animation_cache = NULL;
           image_error ("Imagemagick pixel iterator creation failed",
                        Qnil, Qnil);
           return NULL;
         }
 
+      /* The sub-image may not start at origo, so move the destination
+         iterator to where the sub-image should start. */
+      PixelSetIteratorRow (dest_iterator, source_top);
+
       while ((source = PixelGetNextIteratorRow (source_iterator, &source_width))
              != NULL)
         {
@@ -7929,6 +7954,10 @@ imagemagick_compute_animated_image (MagickWand *super_wand, int ino)
           dest = PixelGetNextIteratorRow (dest_iterator, &dest_width);
           for (x = 0; x < source_width; x++)
             {
+              /* Sanity check.  This shouldn't happen, but apparently
+                 does in some pictures.  */
+              if (x + source_left > dest_width)
+                break;
               /* Normally we only copy over non-transparent pixels,
                  but if the disposal method is "Background", then we
                  copy over all pixels.  */
@@ -7936,7 +7965,7 @@ imagemagick_compute_animated_image (MagickWand *super_wand, int ino)
                   PixelGetAlpha (source[x]))
                 {
                   PixelGetMagickColor (source[x], &pixel);
-                  PixelSetMagickColor (dest[x], &pixel);
+                  PixelSetMagickColor (dest[x + source_left], &pixel);
                 }
             }
           PixelSyncIterator(dest_iterator);