Support for "Do not blend" in mux and demux libraries

Change-Id: I9566a8e2d059fe1ebd9ca99c7e13311bf3f8f281

src/webp/demux.h

@@ -140,8 +140,9 @@ struct WebPIterator {
   WebPData fragment;  // The frame or fragment given by 'frame_num' and
                       // 'fragment_num'.
   int has_alpha;      // True if the frame or fragment contains transparency.
+  WebPMuxAnimBlend blend_method;  // Blend operation for the frame.
 
-  uint32_t pad[3];         // padding for later use.
+  uint32_t pad[2];         // padding for later use.
   void* private_;          // for internal use only.
 };
 

src/webp/mux.h

@@ -199,7 +199,8 @@ struct WebPMuxFrameInfo {
   WebPChunkId id;         // frame type: should be one of WEBP_CHUNK_ANMF,
                           // WEBP_CHUNK_FRGM or WEBP_CHUNK_IMAGE
   WebPMuxAnimDispose dispose_method;  // Disposal method for the frame.
-  uint32_t    pad[2];     // padding for later use
+  WebPMuxAnimBlend   blend_method;    // Blend operation for the frame.
+  uint32_t    pad[1];     // padding for later use
 };
 
 // Sets the (non-animated and non-fragmented) image in the mux object.

src/webp/mux_types.h

@@ -26,6 +26,7 @@ extern "C" {
 // the types are left here for reference.
 // typedef enum WebPFeatureFlags WebPFeatureFlags;
 // typedef enum WebPMuxAnimDispose WebPMuxAnimDispose;
+// typedef enum WebPMuxAnimBlend WebPMuxAnimBlend;
 typedef struct WebPData WebPData;
 
 // VP8X Feature Flags.
@@ -45,6 +46,13 @@ typedef enum WebPMuxAnimDispose {
   WEBP_MUX_DISPOSE_BACKGROUND  // Dispose to background color.
 } WebPMuxAnimDispose;
 
+// Blend operation (animation only). Indicates how transparent pixels of the
+// current frame are blended with those of the previous canvas.
+typedef enum WebPMuxAnimBlend {
+  WEBP_MUX_BLEND,              // Blend.
+  WEBP_MUX_NO_BLEND            // Do not blend.
+} WebPMuxAnimBlend;
+
 // Data type used to describe 'raw' data, e.g., chunk data
 // (ICC profile, metadata) and WebP compressed image data.
 struct WebPData {