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

Change-Id: I9566a8e2d059fe1ebd9ca99c7e13311bf3f8f281

examples/webpmux.c

@@ -430,6 +430,8 @@ static int ParseFrameArgs(const char* args, WebPMuxFrameInfo* const info) {
   // Note: The sanity of the following conversion is checked by
   // WebPMuxSetAnimationParams().
   info->dispose_method = (WebPMuxAnimDispose)dispose_method;
+  // TODO(urvang): Add support for parsing blending method too.
+  info->blend_method = WEBP_MUX_BLEND;
   return 1;
 }
 

src/demux/demux.c

@@ -50,6 +50,7 @@ typedef struct Frame {
   int has_alpha_;
   int duration_;
   WebPMuxAnimDispose dispose_method_;
+  WebPMuxAnimBlend blend_method_;
   int is_fragment_;  // this is a frame fragment (and not a full frame).
   int frame_num_;  // the referent frame number for use in assembling fragments.
   int complete_;   // img_components_ contains a full image.
@@ -303,6 +304,7 @@ static ParseStatus ParseAnimationFrame(
   const int has_frames = !!(dmux->feature_flags_ & ANIMATION_FLAG);
   const uint32_t anmf_payload_size = frame_chunk_size - ANMF_CHUNK_SIZE;
   int added_frame = 0;
+  int bits;
   MemBuffer* const mem = &dmux->mem_;
   Frame* frame;
   ParseStatus status =
@@ -314,7 +316,10 @@ static ParseStatus ParseAnimationFrame(
   frame->width_          = 1 + ReadLE24s(mem);
   frame->height_         = 1 + ReadLE24s(mem);
   frame->duration_       = ReadLE24s(mem);
-  frame->dispose_method_ = (WebPMuxAnimDispose)(ReadByte(mem) & 1);
+  bits = ReadByte(mem);
+  frame->dispose_method_ =
+      (bits & 1) ? WEBP_MUX_DISPOSE_BACKGROUND : WEBP_MUX_DISPOSE_NONE;
+  frame->blend_method_ = (bits & 2) ? WEBP_MUX_NO_BLEND : WEBP_MUX_BLEND;
   if (frame->width_ * (uint64_t)frame->height_ >= MAX_IMAGE_AREA) {
     free(frame);
     return PARSE_ERROR;
@@ -845,6 +850,7 @@ static int SynthesizeFrame(const WebPDemuxer* const dmux,
   iter->has_alpha      = fragment->has_alpha_;
   iter->duration       = fragment->duration_;
   iter->dispose_method = fragment->dispose_method_;
+  iter->blend_method   = fragment->blend_method_;
   iter->complete       = fragment->complete_;
   iter->fragment.bytes = payload;
   iter->fragment.size  = payload_size;

src/mux/muxedit.c

@@ -116,7 +116,9 @@ static WebPMuxError CreateFrameFragmentData(
     PutLE24(frame_frgm_bytes + 6, width - 1);
     PutLE24(frame_frgm_bytes + 9, height - 1);
     PutLE24(frame_frgm_bytes + 12, info->duration);
-    frame_frgm_bytes[15] = (info->dispose_method & 1);
+    frame_frgm_bytes[15] =
+        (info->blend_method == WEBP_MUX_NO_BLEND ? 2 : 0) |
+        (info->dispose_method == WEBP_MUX_DISPOSE_BACKGROUND ? 1 : 0);
   }
 
   frame_frgm->bytes = frame_frgm_bytes;
@@ -310,7 +312,8 @@ WebPMuxError WebPMuxPushFrame(WebPMux* mux, const WebPMuxFrameInfo* frame,
     tmp.y_offset &= ~1;
     if (!is_frame) {  // Reset unused values.
       tmp.duration = 1;
-      tmp.dispose_method = 0;
+      tmp.dispose_method = WEBP_MUX_DISPOSE_NONE;
+      tmp.blend_method = WEBP_MUX_BLEND;
     }
     if (tmp.x_offset < 0 || tmp.x_offset >= MAX_POSITION_OFFSET ||
         tmp.y_offset < 0 || tmp.y_offset >= MAX_POSITION_OFFSET ||

src/mux/muxread.c

@@ -426,6 +426,8 @@ static WebPMuxError MuxGetImageInternal(const WebPMuxImage* const wpi,
   info->x_offset = 0;
   info->y_offset = 0;
   info->duration = 1;
+  info->dispose_method = WEBP_MUX_DISPOSE_NONE;
+  info->blend_method = WEBP_MUX_BLEND;
   // Extract data for related fields.
   info->id = ChunkGetIdFromTag(wpi->img_->tag_);
   return SynthesizeBitstream(wpi, &info->bitstream);
@@ -446,10 +448,17 @@ static WebPMuxError MuxGetFrameFragmentInternal(const WebPMuxImage* const wpi,
   // Extract info.
   frame->x_offset = 2 * GetLE24(frame_frgm_data->bytes + 0);
   frame->y_offset = 2 * GetLE24(frame_frgm_data->bytes + 3);
-  frame->duration = is_frame ? GetLE24(frame_frgm_data->bytes + 12) : 1;
-  frame->dispose_method =
-      is_frame ? (WebPMuxAnimDispose)(frame_frgm_data->bytes[15] & 1)
-               : WEBP_MUX_DISPOSE_NONE;
+  if (is_frame) {
+    const uint8_t bits = frame_frgm_data->bytes[15];
+    frame->duration = GetLE24(frame_frgm_data->bytes + 12);
+    frame->dispose_method =
+        (bits & 1) ? WEBP_MUX_DISPOSE_BACKGROUND : WEBP_MUX_DISPOSE_NONE;
+    frame->blend_method = (bits & 2) ? WEBP_MUX_NO_BLEND : WEBP_MUX_BLEND;
+  } else {  // Defaults for unused values.
+    frame->duration = 1;
+    frame->dispose_method = WEBP_MUX_DISPOSE_NONE;
+    frame->blend_method = WEBP_MUX_BLEND;
+  }
   frame->id = ChunkGetIdFromTag(wpi->header_->tag_);
   return SynthesizeBitstream(wpi, &frame->bitstream);
 }

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 {