Alternate between two SkBitmaps in SkAnimatedImage

Bug: 78866720

The client in Android calls newPictureSnapshot, which results in copying
the mutable SkBitmap into a newly allocated one in each frame. Avoid
this by calling SkMakeImageFromRasterBitmap with
kNever_SkCopyPixelsMode. Make SkAnimatedImage copy on write, by copying
before decoding if the bitmap's pixel ref is not unique.

Android's AnimatedImageDrawable's current architecture only decodes one
frame in advance, so it will never need to perform the copy on write.
This will save one bitmap allocation per GIF frame.

Add a test to verify that copy on write works as expected.

Change-Id: I87eb6e84089096cd2d618b91fb627fc58677e66a
Reviewed-on: https://skia-review.googlesource.com/129841
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
Auto-Submit: Leon Scroggins <scroggo@google.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/include/android/SkAnimatedImage.h b/include/android/SkAnimatedImage.h
index 51f0e5b84b..983a57bd5c 100644
--- a/include/android/SkAnimatedImage.h
+++ b/include/android/SkAnimatedImage.h
@@ -107,7 +107,20 @@ private:
         int      fIndex;
         SkCodecAnimation::DisposalMethod fDisposalMethod;
 
+        // init() may have to create a new SkPixelRef, if the
+        // current one is already in use by another owner (e.g.
+        // an SkPicture). This determines whether to copy the
+        // existing one to the new one.
+        enum class OnInit {
+            // Restore the image from the old SkPixelRef to the
+            // new one.
+            kRestoreIfNecessary,
+            // No need to restore.
+            kNoRestore,
+        };
+
         Frame();
+        bool init(const SkImageInfo& info, OnInit);
         bool copyTo(Frame*) const;
     };
 
@@ -122,7 +135,8 @@ private:
 
     bool                            fFinished;
     int                             fCurrentFrameDuration;
-    Frame                           fActiveFrame;
+    Frame                           fDisplayFrame;
+    Frame                           fDecodingFrame;
     Frame                           fRestoreFrame;
     int                             fRepetitionCount;
     int                             fRepetitionsCompleted;