Tell CG ImageEncoder that a bitmap is opaque if it is.

Review URL: https://codereview.appspot.com/6819110

git-svn-id: http://skia.googlecode.com/svn/trunk@6378 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 25 insertions, 5 deletions

diff --git a/src/utils/mac/SkCreateCGImageRef.cpp b/src/utils/mac/SkCreateCGImageRef.cpp
index df20ba930d..abad8cb440 100644
--- a/src/utils/mac/SkCreateCGImageRef.cpp
+++ b/src/utils/mac/SkCreateCGImageRef.cpp
@@ -36,31 +36,51 @@ static bool getBitmapInfo(const SkBitmap& bm,
             *bitsPerComponent = 8;
 #if defined(SK_CPU_LENDIAN) && HAS_ARGB_SHIFTS(24, 0, 8, 16) \
 || defined(SK_CPU_BENDIAN) && HAS_ARGB_SHIFTS(0, 24, 16, 8)
-            *info = kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast;
+            *info = kCGBitmapByteOrder32Big;
+            if (bm.isOpaque()) {
+                *info |= kCGImageAlphaNoneSkipLast;
+            } else {
+                *info |= kCGImageAlphaPremultipliedLast;
+            }
 #elif defined(SK_CPU_LENDIAN) && HAS_ARGB_SHIFTS(24, 16, 8, 0) \
 || defined(SK_CPU_BENDIAN) && HAS_ARGB_SHIFTS(24, 16, 8, 0)
             // Matches the CGBitmapInfo that Apple recommends for best
             // performance, used by google chrome.
-            *info = kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst;
+            *info = kCGBitmapByteOrder32Little;
+            if (bm.isOpaque()) {
+                *info |= kCGImageAlphaNoneSkipFirst;
+            } else {
+                *info |= kCGImageAlphaPremultipliedFirst;
+            }
 #else
             // ...add more formats as required...
 #warning Cannot convert SkBitmap to CGImageRef with these shiftmasks. \
 This will probably not work.
             // Legacy behavior. Perhaps turn this into an error at some
             // point.
-            *info = kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast;
+            *info = kCGBitmapByteOrder32Big;
+            if (bm.isOpaque()) {
+                *info |= kCGImageAlphaNoneSkipLast;
+            } else {
+                *info |= kCGImageAlphaPremultipliedLast;
+            }
 #endif
             break;
 #if 0
         case SkBitmap::kRGB_565_Config:
             // doesn't see quite right. Are they thinking 1555?
             *bitsPerComponent = 5;
-            *info = kCGBitmapByteOrder16Little;
+            *info = kCGBitmapByteOrder16Little | kCGImageAlphaNone;
             break;
 #endif
         case SkBitmap::kARGB_4444_Config:
             *bitsPerComponent = 4;
-            *info = kCGBitmapByteOrder16Little | kCGImageAlphaPremultipliedLast;
+            *info = kCGBitmapByteOrder16Little;
+            if (bm.isOpaque()) {
+                *info |= kCGImageAlphaNoneSkipLast;
+            } else {
+                *info |= kCGImageAlphaPremultipliedLast;
+            }
             break;
         default:
             return false;