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, 81 insertions, 121 deletions

diff --git a/third_party/gif/SkGifImageReader.cpp b/third_party/gif/SkGifImageReader.cpp
index 8c5cfa1ea8..0666fedbc8 100644
--- a/third_party/gif/SkGifImageReader.cpp
+++ b/third_party/gif/SkGifImageReader.cpp
@@ -131,19 +131,19 @@ bool SkGIFLZWContext::outputRow(const unsigned char* rowBegin)
         drowEnd = drowStart + rowDup;
 
         // Extend if bottom edge isn't covered because of the shift upward.
-        if (((m_frameContext->height() - 1) - drowEnd) <= rowShift)
+        if ((unsigned)((m_frameContext->height() - 1) - drowEnd) <= rowShift)
             drowEnd = m_frameContext->height() - 1;
 
         // Clamp first and last rows to upper and lower edge of image.
         if (drowStart < 0)
             drowStart = 0;
 
-        if ((unsigned)drowEnd >= m_frameContext->height())
+        if (drowEnd >= m_frameContext->height())
             drowEnd = m_frameContext->height() - 1;
     }
 
     // Protect against too much image data.
-    if ((unsigned)drowStart >= m_frameContext->height())
+    if (drowStart >= m_frameContext->height())
         return true;
 
     // CALLBACK: Let the client know we have decoded a row.
@@ -159,7 +159,7 @@ bool SkGIFLZWContext::outputRow(const unsigned char* rowBegin)
             switch (ipass) {
             case 1:
                 irow += 8;
-                if (irow >= m_frameContext->height()) {
+                if (irow >= (unsigned) m_frameContext->height()) {
                     ipass++;
                     irow = 4;
                 }
@@ -167,7 +167,7 @@ bool SkGIFLZWContext::outputRow(const unsigned char* rowBegin)
 
             case 2:
                 irow += 8;
-                if (irow >= m_frameContext->height()) {
+                if (irow >= (unsigned) m_frameContext->height()) {
                     ipass++;
                     irow = 2;
                 }
@@ -175,7 +175,7 @@ bool SkGIFLZWContext::outputRow(const unsigned char* rowBegin)
 
             case 3:
                 irow += 4;
-                if (irow >= m_frameContext->height()) {
+                if (irow >= (unsigned) m_frameContext->height()) {
                     ipass++;
                     irow = 1;
                 }
@@ -183,7 +183,7 @@ bool SkGIFLZWContext::outputRow(const unsigned char* rowBegin)
 
             case 4:
                 irow += 2;
-                if (irow >= m_frameContext->height()) {
+                if (irow >= (unsigned) m_frameContext->height()) {
                     ipass++;
                     irow = 0;
                 }
@@ -192,7 +192,7 @@ bool SkGIFLZWContext::outputRow(const unsigned char* rowBegin)
             default:
                 break;
             }
-        } while (irow > (m_frameContext->height() - 1));
+        } while (irow > (unsigned) (m_frameContext->height() - 1));
     }
     return true;
 }
@@ -491,8 +491,8 @@ bool SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
             // screen.
             // Note that we don't inform the client of the size yet, as it might
             // change after we read the first frame's image header.
-            m_screenWidth = GETINT16(currentComponent);
-            m_screenHeight = GETINT16(currentComponent + 2);
+            fScreenWidth = GETINT16(currentComponent);
+            fScreenHeight = GETINT16(currentComponent + 2);
 
             const int globalColorMapColors = 2 << (currentComponent[4] & 0x07);
 
@@ -623,7 +623,7 @@ bool SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
                 currentFrame->setDisposalMethod(SkCodecAnimation::Keep_DisposalMethod);
                 break;
             }
-            currentFrame->setDelayTime(GETINT16(currentComponent + 1) * 10);
+            currentFrame->setDuration(GETINT16(currentComponent + 1) * 10);
             GETN(1, SkGIFConsumeBlock);
             break;
         }
@@ -706,7 +706,7 @@ bool SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
         }
 
         case SkGIFImageHeader: {
-            unsigned height, width, xOffset, yOffset;
+            int height, width, xOffset, yOffset;
             const unsigned char* currentComponent =
                 reinterpret_cast<const unsigned char*>(m_streamBuffer.get());
 
@@ -730,8 +730,8 @@ bool SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
             // set to zero, since usually the first frame completely fills
             // the image.
             if (currentFrameIsFirstFrame()) {
-                m_screenHeight = std::max(m_screenHeight, yOffset + height);
-                m_screenWidth = std::max(m_screenWidth, xOffset + width);
+                fScreenHeight = std::max(fScreenHeight, yOffset + height);
+                fScreenWidth = std::max(fScreenWidth, xOffset + width);
             }
 
             // NOTE: Chromium placed this block after setHeaderDefined, down
@@ -743,8 +743,8 @@ bool SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
             // Work around more broken GIF files that have zero image width or
             // height.
             if (!height || !width) {
-                height = m_screenHeight;
-                width = m_screenWidth;
+                height = fScreenHeight;
+                width = fScreenWidth;
                 if (!height || !width) {
                     // This prevents attempting to continue reading this invalid stream.
                     GETN(0, SkGIFDone);
@@ -756,13 +756,17 @@ bool SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
             // The three low-order bits of currentComponent[8] specify the bits per pixel.
             const int numColors = 2 << (currentComponent[8] & 0x7);
             if (currentFrameIsFirstFrame()) {
-                if (hasTransparentPixel(0, isLocalColormapDefined, numColors)) {
+                const int transPix = m_frames.empty() ? SkGIFColorMap::kNotFound
+                                                      : m_frames[0]->transparentPixel();
+                if (this->hasTransparency(transPix,
+                        isLocalColormapDefined, numColors))
+                {
                     m_firstFrameHasAlpha = true;
                     m_firstFrameSupportsIndex8 = true;
                 } else {
                     const bool frameIsSubset = xOffset > 0 || yOffset > 0
-                            || xOffset + width < m_screenWidth
-                            || yOffset + height < m_screenHeight;
+                            || width < fScreenWidth
+                            || height < fScreenHeight;
                     m_firstFrameHasAlpha = frameIsSubset;
                     m_firstFrameSupportsIndex8 = !frameIsSubset;
                 }
@@ -780,7 +784,7 @@ bool SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
             }
 
 
-            currentFrame->setRect(xOffset, yOffset, width, height);
+            currentFrame->setXYWH(xOffset, yOffset, width, height);
             currentFrame->setInterlaced(SkToBool(currentComponent[8] & 0x40));
 
             // Overlaying interlaced, transparent GIFs over
@@ -852,20 +856,14 @@ bool SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
     return true;
 }
 
-bool SkGifImageReader::hasTransparentPixel(int i, bool isLocalColormapDefined,
-                                           int localColors) {
-    SkASSERT(i >= 0);
-    if (m_frames.size() <= static_cast<size_t>(i)) {
-        // This should only happen when parsing the first frame.
-        SkASSERT(0 == i);
-
-        // We did not see a Graphics Control Extension, so no transparent
-        // pixel was specified. But if there is no color table, this frame is
-        // still transparent.
-        return !isLocalColormapDefined && m_globalColorMap.numColors() == 0;
+bool SkGifImageReader::hasTransparency(int transparentPixel, bool isLocalColormapDefined,
+                                       int localColors) const {
+    const int globalColors = m_globalColorMap.numColors();
+    if (!isLocalColormapDefined && globalColors == 0) {
+        // No color table for this frame, so it is completely transparent.
+        return true;
     }
 
-    const int transparentPixel = m_frames[i]->transparentPixel();
     if (transparentPixel < 0) {
         SkASSERT(SkGIFColorMap::kNotFound == transparentPixel);
         return false;
@@ -875,16 +873,9 @@ bool SkGifImageReader::hasTransparentPixel(int i, bool isLocalColormapDefined,
         return transparentPixel < localColors;
     }
 
-    const int globalColors = m_globalColorMap.numColors();
-    if (!globalColors) {
-        // No color table for this frame, so the frame is empty.
-        // This is technically different from having a transparent
-        // pixel, but we'll treat it the same - nothing to draw here.
-        return true;
-    }
-
     // If there is a global color table, it will be parsed before reaching
     // here. If its numColors is set, it will be defined.
+    SkASSERT(globalColors > 0);
     SkASSERT(m_globalColorMap.isDefined());
     return transparentPixel < globalColors;
 }
@@ -893,7 +884,7 @@ void SkGifImageReader::addFrameIfNecessary()
 {
     if (m_frames.empty() || m_frames.back()->isComplete()) {
         const size_t i = m_frames.size();
-        std::unique_ptr<SkGIFFrameContext> frame(new SkGIFFrameContext(static_cast<int>(i)));
+        std::unique_ptr<SkGIFFrameContext> frame(new SkGIFFrameContext(this, static_cast<int>(i)));
         m_frames.push_back(std::move(frame));
     }
 }
@@ -907,38 +898,43 @@ static SkIRect frame_rect_on_screen(SkIRect frameRect,
     return frameRect;
 }
 
-static bool independent(const SkGIFFrameContext& frame) {
+static bool independent(const SkFrame& frame) {
     return frame.getRequiredFrame() == SkCodec::kNone;
 }
 
-static bool restore_bg(const SkGIFFrameContext& frame) {
+static bool restore_bg(const SkFrame& frame) {
     return frame.getDisposalMethod() == SkCodecAnimation::RestoreBGColor_DisposalMethod;
 }
 
-void SkGifImageReader::setAlphaAndRequiredFrame(SkGIFFrameContext* frame) {
+bool SkGIFFrameContext::onReportsAlpha() const {
+    // Note: We could correct these after decoding - i.e. some frames may turn out to be
+    // independent and opaque if they do not use the transparent pixel, but that would require
+    // checking whether each pixel used the transparent index.
+    return m_owner->hasTransparency(this->transparentPixel(),
+            m_localColorMap.isDefined(), m_localColorMap.numColors());
+}
+
+void SkFrameHolder::setAlphaAndRequiredFrame(SkFrame* frame) {
+    const bool reportsAlpha = frame->reportsAlpha();
+    const auto screenRect = SkIRect::MakeWH(fScreenWidth, fScreenHeight);
+    const auto frameRect = frame_rect_on_screen(frame->frameRect(), screenRect);
+
     const int i = frame->frameId();
     if (0 == i) {
-        frame->setHasAlpha(m_firstFrameHasAlpha);
+        frame->setHasAlpha(reportsAlpha || frameRect != screenRect);
         frame->setRequiredFrame(SkCodec::kNone);
         return;
     }
 
-    // Note: We could correct these after decoding - i.e. some frames may turn out to be
-    // independent and opaque if they do not use the transparent pixel, but that would require
-    // checking whether each pixel used the transparent index.
-    const SkGIFColorMap& localMap = frame->localColorMap();
-    const bool transValid = hasTransparentPixel(i, localMap.isDefined(), localMap.numColors());
-
-    const auto screenRect = SkIRect::MakeWH(m_screenWidth, m_screenHeight);
-    const auto frameRect = frame_rect_on_screen(frame->frameRect(), screenRect);
 
-    if (!transValid && frameRect == screenRect) {
-        frame->setHasAlpha(false);
+    const bool blendWithPrevFrame = frame->getBlend() == SkCodecAnimation::Blend::kPriorFrame;
+    if ((!reportsAlpha || !blendWithPrevFrame) && frameRect == screenRect) {
+        frame->setHasAlpha(reportsAlpha);
         frame->setRequiredFrame(SkCodec::kNone);
         return;
     }
 
-    const SkGIFFrameContext* prevFrame = m_frames[i - 1].get();
+    const SkFrame* prevFrame = this->getFrame(i-1);
     while (prevFrame->getDisposalMethod() == SkCodecAnimation::RestorePrevious_DisposalMethod) {
         const int prevId = prevFrame->frameId();
         if (0 == prevId) {
@@ -947,7 +943,7 @@ void SkGifImageReader::setAlphaAndRequiredFrame(SkGIFFrameContext* frame) {
             return;
         }
 
-        prevFrame = m_frames[prevId - 1].get();
+        prevFrame = this->getFrame(prevId - 1);
     }
 
     const bool clearPrevFrame = restore_bg(*prevFrame);
@@ -961,7 +957,7 @@ void SkGifImageReader::setAlphaAndRequiredFrame(SkGIFFrameContext* frame) {
         }
     }
 
-    if (transValid) {
+    if (reportsAlpha && blendWithPrevFrame) {
         // Note: We could be more aggressive here. If prevFrame clears
         // to background color and covers its required frame (and that
         // frame is independent), prevFrame could be marked independent.
@@ -979,7 +975,7 @@ void SkGifImageReader::setAlphaAndRequiredFrame(SkGIFFrameContext* frame) {
             return;
         }
 
-        prevFrame = m_frames[prevRequiredFrame].get();
+        prevFrame = this->getFrame(prevRequiredFrame);
         prevFrameRect = frame_rect_on_screen(prevFrame->frameRect(), screenRect);
     }
 
@@ -998,7 +994,7 @@ void SkGifImageReader::setAlphaAndRequiredFrame(SkGIFFrameContext* frame) {
 
     SkASSERT(prevFrame->getDisposalMethod() == SkCodecAnimation::Keep_DisposalMethod);
     frame->setRequiredFrame(prevFrame->frameId());
-    frame->setHasAlpha(prevFrame->hasAlpha());
+    frame->setHasAlpha(prevFrame->hasAlpha() || (reportsAlpha && !blendWithPrevFrame));
 }
 
 // FIXME: Move this method to close to doLZW().
diff --git a/third_party/gif/SkGifImageReader.h b/third_party/gif/SkGifImageReader.h
index 4667f7963f..6c313e923b 100644
--- a/third_party/gif/SkGifImageReader.h
+++ b/third_party/gif/SkGifImageReader.h
@@ -47,6 +47,7 @@ class SkGifCodec;
 #include "SkCodecAnimation.h"
 #include "SkColorTable.h"
 #include "SkData.h"
+#include "SkFrameHolder.h"
 #include "SkImageInfo.h"
 #include "SkStreamBuffer.h"
 #include "../private/SkTArray.h"
@@ -85,7 +86,7 @@ enum SkGIFState {
     SkGIFConsumeComment
 };
 
-struct SkGIFFrameContext;
+class SkGIFFrameContext;
 class SkGIFColorMap;
 
 // LZW decoder state machine.
@@ -191,19 +192,15 @@ private:
     mutable sk_sp<SkColorTable> m_table;
 };
 
+class SkGifImageReader;
+
 // LocalFrame output state machine.
-struct SkGIFFrameContext : SkNoncopyable {
+class SkGIFFrameContext : public SkFrame {
 public:
-    SkGIFFrameContext(int id)
-        : m_frameId(id)
-        , m_xOffset(0)
-        , m_yOffset(0)
-        , m_width(0)
-        , m_height(0)
+    SkGIFFrameContext(SkGifImageReader* reader, int id)
+        : INHERITED(id)
+        , m_owner(reader)
         , m_transparentPixel(SkGIFColorMap::kNotFound)
-        , m_hasAlpha(false)
-        , m_disposalMethod(SkCodecAnimation::Keep_DisposalMethod)
-        , m_requiredFrame(kUninitialized)
         , m_dataSize(0)
         , m_progressiveDisplay(false)
         , m_interlaced(false)
@@ -226,31 +223,8 @@ public:
 
     bool decode(SkStreamBuffer*, SkGifCodec* client, bool* frameDecoded);
 
-    int frameId() const { return m_frameId; }
-    void setRect(unsigned x, unsigned y, unsigned width, unsigned height)
-    {
-        m_xOffset = x;
-        m_yOffset = y;
-        m_width = width;
-        m_height = height;
-    }
-    SkIRect frameRect() const { return SkIRect::MakeXYWH(m_xOffset, m_yOffset, m_width, m_height); }
-    unsigned xOffset() const { return m_xOffset; }
-    unsigned yOffset() const { return m_yOffset; }
-    unsigned width() const { return m_width; }
-    unsigned height() const { return m_height; }
     int transparentPixel() const { return m_transparentPixel; }
     void setTransparentPixel(int pixel) { m_transparentPixel = pixel; }
-    bool hasAlpha() const { return m_hasAlpha; }
-    void setHasAlpha(bool alpha) { m_hasAlpha = alpha; }
-    SkCodecAnimation::DisposalMethod getDisposalMethod() const { return m_disposalMethod; }
-    void setDisposalMethod(SkCodecAnimation::DisposalMethod disposalMethod) { m_disposalMethod = disposalMethod; }
-
-    int getRequiredFrame() const {
-        SkASSERT(this->reachedStartOfData());
-        return m_requiredFrame;
-    }
-    void setRequiredFrame(int req) { m_requiredFrame = req; }
 
     unsigned delayTime() const { return m_delayTime; }
     void setDelayTime(unsigned delay) { m_delayTime = delay; }
@@ -274,24 +248,14 @@ public:
     const SkGIFColorMap& localColorMap() const { return m_localColorMap; }
     SkGIFColorMap& localColorMap() { return m_localColorMap; }
 
-    bool reachedStartOfData() const { return m_requiredFrame != kUninitialized; }
+protected:
+    bool onReportsAlpha() const override;
 
 private:
-    static constexpr int kUninitialized = -2;
+    // Unowned pointer to the object that owns this frame.
+    const SkGifImageReader* m_owner;
 
-    int m_frameId;
-    unsigned m_xOffset;
-    unsigned m_yOffset; // With respect to "screen" origin.
-    unsigned m_width;
-    unsigned m_height;
     int m_transparentPixel; // Index of transparent pixel. Value is kNotFound if there is no transparent pixel.
-    // Cached value, taking into account:
-    // - m_transparentPixel
-    // - frameRect
-    // - previous required frame
-    bool m_hasAlpha;
-    SkCodecAnimation::DisposalMethod m_disposalMethod; // Restore to background, leave in place, etc.
-    int m_requiredFrame;
     int m_dataSize;
 
     bool m_progressiveDisplay; // If true, do Haeberli interlace hack.
@@ -309,9 +273,11 @@ private:
     bool m_isComplete;
     bool m_isHeaderDefined;
     bool m_isDataSizeDefined;
+
+    typedef SkFrame INHERITED;
 };
 
-class SkGifImageReader final : public SkNoncopyable {
+class SkGifImageReader final : public SkFrameHolder {
 public:
     // This takes ownership of stream.
     SkGifImageReader(SkStream* stream)
@@ -319,8 +285,6 @@ public:
         , m_state(SkGIFType)
         , m_bytesToConsume(6) // Number of bytes for GIF type, either "GIF87a" or "GIF89a".
         , m_version(0)
-        , m_screenWidth(0)
-        , m_screenHeight(0)
         , m_loopCount(cLoopCountNotSeen)
         , m_streamBuffer(stream)
         , m_parseCompleted(false)
@@ -335,9 +299,6 @@ public:
 
     void setClient(SkGifCodec* client) { m_client = client; }
 
-    unsigned screenWidth() const { return m_screenWidth; }
-    unsigned screenHeight() const { return m_screenHeight; }
-
     // Option to pass to parse(). All enums are negative, because a non-negative value is used to
     // indicate that the Reader should parse up to and including the frame indicated.
     enum SkGIFParseQuery {
@@ -408,6 +369,16 @@ public:
 
     bool firstFrameSupportsIndex8() const { return m_firstFrameSupportsIndex8; }
 
+    // Helper function that returns whether an SkGIFFrameContext has transparency.
+    // This method is sometimes called before creating one/parsing its color map,
+    // so it cannot rely on SkGIFFrameContext::transparentPixel or ::localColorMap().
+    bool hasTransparency(int transPix, bool hasLocalColorMap, int localMapColors) const;
+
+protected:
+    const SkFrame* onGetFrame(int i) const override {
+        return static_cast<const SkFrame*>(this->frameContext(i));
+    }
+
 private:
     // Requires that one byte has been buffered into m_streamBuffer.
     unsigned char getOneByte() const {
@@ -415,11 +386,6 @@ private:
     }
 
     void addFrameIfNecessary();
-    // Must be called *after* the SkGIFFrameContext's color table (if any) has been parsed.
-    void setAlphaAndRequiredFrame(SkGIFFrameContext*);
-    // This method is sometimes called before creating a SkGIFFrameContext, so it cannot rely
-    // on SkGIFFrameContext::localColorMap().
-    bool hasTransparentPixel(int frameIndex, bool hasLocalColorMap, int localMapColors);
     bool currentFrameIsFirstFrame() const
     {
         return m_frames.empty() || (m_frames.size() == 1u && !m_frames[0]->isComplete());
@@ -434,8 +400,6 @@ private:
 
     // Global (multi-image) state.
     int m_version; // Either 89 for GIF89 or 87 for GIF87.
-    unsigned m_screenWidth; // Logical screen width & height.
-    unsigned m_screenHeight;
     SkGIFColorMap m_globalColorMap;
 
     static constexpr int cLoopCountNotSeen = -2;