Add animation support to SkWebpCodec

TBR=reed@google.com
(No change to the public API, but changed a header file)

SkWebpCodec:
- Implement onGetFrameCount, onGetFrameInfo, and onGetRepetitionCount
- Respect the alpha reported by libwebp. Although the spec states that
  it is only a hint, the libwebp encoder uses it properly. Respecting
  allows us to draw opaque images faster and decode them to 565. This
  also matches other SkCodecs (and Chromium).
- onGetPixels:
  - Decode the frame requested, recursively decoding required frame if
    necessary
  - When blending with a prior frame, use SkRasterPipeline

SkCodec:
- Move check for negative index to getFrameInfo
- Reset the colorXform if one is not needed

SkCodecAnimation:
- Add new blend enum, for WebP's (and APNG's) non-blending option

SkFrameHolder:
- New base classes for frames and the owner of the frames, allowing
  code sharing between SkWebpCodec and SkGifCodec (particularly for
  determining whether a frame has alpha and what frame it depends on)
- When moving items from SkGIFFrameContext, use Skia conventions (i.e.
  int instead of unsigned)
- Rename "delay time" to "duration", to match e.g. SkFrameInfo::
  fDuration

SkGifImageReader:
- Move pieces to SkFrameHolder, and adapt to changes made in the
  process
- Make setAlphaAndRequiredFrame (now on the base class SkFrameHolder)
  more general to support webp, and add support for frames that do not
  blend
- Change SkGIFFrameContext from a struct to a class, to match how we
  use the distinction elsewhere (i.e. struct is a small object with
  public fields)
- Rework hasTransparentPixel (now hasTransparency, since it returns true
  in some cases where there is not a transparent pixel) to better fit
  with the modified setAlphaAndRequiredFrame. Also be more consistent
  when there is no transparent pixel but no color map.
- Simplify an if condition that was previously simplified in 2d61e717
  but accidentally got reverted in a4db9be6

CodecAnimTest:
- Test new animated webp files
- Rearrange the test to more cleanly print alpha type mismatches for
  the first frame

resources:
- webp-animated.webp
  - animated webp from Chromium
- blendBG.webp
  - new webp file using bits of webp-animated-semitransparent4.webp
    from Chromium
  - tests required frame and alpha when using the non-blending mode
  - frames have the following properties:
    - Frame 0: no alpha, fills screen
    - Frame 1: alpha, fills screen
    - Frame 2: no alpha, fills screen
    - Frame 3: alpha, fills screen, blendBG
    - Frame 4: no alpha, fills screen, blendBG
    - Frame 5: alpha, blendBG
    - Frame 6: covers 4, has alpha, blendBG
  - also used to test decoding to 565 if the new frame data has alpha
    but blends onto an opaque frame

DM.cpp:
- Test animated images to non-native 8888 and unpremul

DMSrcSink.cpp:
- Do not test non-native 8888 decodes to f16 dst
- Test unpremul decodes to f16
- Copy a frame of an animated image prior to drawing, since in unpremul
  mode, the DM code will premultiply first.

Bug: skia: 3315
Change-Id: I4e55ae2ee5bc095b37a743bdcfac644be603b980
Reviewed-on: https://skia-review.googlesource.com/16707
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>

2 files changed, 20 insertions, 16 deletions

diff --git a/dm/DM.cpp b/dm/DM.cpp
index aa2b081fb1..2f7dd21e34 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -603,8 +603,12 @@ static void push_codec_srcs(Path path) {
     {
         std::vector<SkCodec::FrameInfo> frameInfos = codec->getFrameInfo();
         if (frameInfos.size() > 1) {
-            push_codec_src(path, CodecSrc::kAnimated_Mode, CodecSrc::kGetFromCanvas_DstColorType,
-                           kPremul_SkAlphaType, 1.0f);
+            for (auto dstCT : { CodecSrc::kNonNative8888_Always_DstColorType,
+                    CodecSrc::kGetFromCanvas_DstColorType }) {
+                for (auto at : { kUnpremul_SkAlphaType, kPremul_SkAlphaType }) {
+                    push_codec_src(path, CodecSrc::kAnimated_Mode, dstCT, at, 1.0f);
+                }
+            }
         }
 
     }
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index 752ab2e4ae..8979d2d285 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -364,7 +364,8 @@ static bool get_decode_info(SkImageInfo* decodeInfo, SkColorType canvasColorType
             *decodeInfo = decodeInfo->makeColorType(kGray_8_SkColorType);
             break;
         case CodecSrc::kNonNative8888_Always_DstColorType:
-            if (kRGB_565_SkColorType == canvasColorType) {
+            if (kRGB_565_SkColorType == canvasColorType
+                    || kRGBA_F16_SkColorType == canvasColorType) {
                 return false;
             }
 #ifdef SK_PMCOLOR_IS_RGBA
@@ -380,11 +381,6 @@ static bool get_decode_info(SkImageInfo* decodeInfo, SkColorType canvasColorType
             }
 
             if (kRGBA_F16_SkColorType == canvasColorType) {
-                if (kUnpremul_SkAlphaType == dstAlphaType) {
-                    // Testing kPremul is enough for adequate coverage of F16 decoding.
-                    return false;
-                }
-
                 sk_sp<SkColorSpace> linearSpace =
                         as_CSB(decodeInfo->colorSpace())->makeLinearGamma();
                 *decodeInfo = decodeInfo->makeColorSpace(std::move(linearSpace));
@@ -499,6 +495,18 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
                 switch (result) {
                     case SkCodec::kSuccess:
                     case SkCodec::kIncompleteInput: {
+                        // If the next frame depends on this one, store it in priorFrame.
+                        // It is possible that we may discard a frame that future frames depend on,
+                        // but the codec will simply redecode the discarded frame.
+                        // Do this before calling draw_to_canvas, which premultiplies in place. If
+                        // we're decoding to unpremul, we want to pass the unmodified frame to the
+                        // codec for decoding the next frame.
+                        if (static_cast<size_t>(i+1) < frameInfos.size()
+                                && frameInfos[i+1].fRequiredFrame == i) {
+                            memcpy(priorFramePixels.reset(safeSize), pixels.get(), safeSize);
+                            cachedFrame = i;
+                        }
+
                         SkAutoCanvasRestore acr(canvas, true);
                         const int xTranslate = (i % factor) * decodeInfo.width();
                         const int yTranslate = (i / factor) * decodeInfo.height();
@@ -521,14 +529,6 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
                         return SkStringPrintf("Couldn't getPixels for frame %i in %s.",
                                               i, fPath.c_str());
                 }
-
-                // If a future frame depends on this one, store it in priorFrame.
-                // (Note that if i+1 does *not* depend on i, then no future frame can.)
-                if (static_cast<size_t>(i+1) < frameInfos.size()
-                        && frameInfos[i+1].fRequiredFrame == i) {
-                    memcpy(priorFramePixels.reset(safeSize), pixels.get(), safeSize);
-                    cachedFrame = i;
-                }
             }
             break;
         }