commit 9d5629025c91f2668eea162e06cb1c869308e113
author Pascal Massimino <pascal.massimino@gmail.com> Tue Jun 24 20:20:29 2014 +0000
committer James Zern <jzern@google.com> Wed Jul 02 21:03:35 2014 -0700
tree 0fea8276ab25f788ec1f6dcfa9813b0603d405eb
parent b8b596f6c3f15d074658e7dac67f8d1603145b9a

make alpha-detection loop in IsKeyFrame() in good x/y order

Change-Id: Ifeeb855e66c7b6b849e8584787dc24e7371b1e67

examples/gif2webp_util.c

diff --git a/examples/gif2webp_util.c b/examples/gif2webp_util.c
index eedad98..e2555f5 100644
--- a/examples/gif2webp_util.c
+++ b/examples/gif2webp_util.c
@@ -166,10 +166,10 @@
 
   // If previous canvas (with previous frame disposed) is all transparent,
   // current frame is a key frame.
-  for (i = 0; i < prev->width; ++i) {
-    for (j = 0; j < prev->height; ++j) {
-      const uint32_t prev_alpha = (prev->argb[j * prev->argb_stride + i]) >> 24;
-      if (prev_alpha != 0) {
+  for (j = 0; j < prev->height; ++j) {
+    const uint32_t* const row = &prev->argb[j * prev->argb_stride];
+    for (i = 0; i < prev->width; ++i) {
+      if (row[i] & 0xff000000u) {   // has alpha?
         is_key_frame = 0;
         break;
       }