Implement ImageBitmap options premultiplyAlpha

third_party/WebKit/Source/core/frame/ImageBitmap.cpp

Index: third_party/WebKit/Source/core/frame/ImageBitmap.cpp
diff --git a/third_party/WebKit/Source/core/frame/ImageBitmap.cpp b/third_party/WebKit/Source/core/frame/ImageBitmap.cpp
index c7348a846eba46ffd10fd41e291155fc90e3dc5f..a17d0fd4f834e9026f5f33a9afb5930b56af5c8d 100644
--- a/third_party/WebKit/Source/core/frame/ImageBitmap.cpp
+++ b/third_party/WebKit/Source/core/frame/ImageBitmap.cpp
@@ -7,13 +7,28 @@
 #include "core/html/HTMLCanvasElement.h"
 #include "core/html/HTMLVideoElement.h"
 #include "core/html/ImageData.h"
+#include "platform/image-decoders/ImageDecoder.h"
 #include "third_party/skia/include/core/SkSurface.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 static const char* imageOrientationFlipY = "flipY";
+static const char* imageBitmapOptionNone = "none";
 
+static void parseOptions(const ImageBitmapOptions& options, bool& imageOrientationFlipYFlag, bool& premultiplyAlphaEnabledFlag)
+{
+    if (options.imageOrientation() == imageOrientationFlipY)
+        imageOrientationFlipYFlag = true;
+    else
+        imageOrientationFlipYFlag = false;

[Justin Novosad, 2016/02/05 14:46:41]

ASSERT(options.imageOrientation() == imageBitmapOptionNone);

[xidachen, 2016/02/05 16:47:36]

Acknowledged.

+    if (options.premultiplyAlpha() == imageBitmapOptionNone)
+        premultiplyAlphaEnabledFlag = false;
+    else
+        premultiplyAlphaEnabledFlag = true;

[Justin Novosad, 2016/02/05 14:46:41]

ASSERT(options.premultiplyAlpha() == premultiplyAlphaDefault);

[xidachen, 2016/02/05 16:47:36]

Acknowledged.

+}
+
+// The following two functions are helpers used in cropImage
 static inline IntRect normalizeRect(const IntRect& rect)
 {
     return IntRect(std::min(rect.x(), rect.maxX()),
@@ -22,7 +37,14 @@ static inline IntRect normalizeRect(const IntRect& rect)
         std::max(rect.height(), -rect.height()));
 }
 
-// TODO(xidachen): this function needs to be changed later on when implementing premultiplyAlpha option
+static bool frameIsValid(const SkBitmap& frameBitmap)
+{
+    return !frameBitmap.isNull()
+        && !frameBitmap.empty()
+        && frameBitmap.isImmutable()
+        && frameBitmap.colorType() == kN32_SkColorType;

[Justin Novosad, 2016/02/05 14:46:41]

Should some of these conditions be ASSERTs (i.e. the ones we don't expect to
ever occur)?

[xidachen, 2016/02/05 16:47:36]

Acknowledged.

+}
+
 static SkImage* flipSkImageVertically(SkImage* input)
 {
     int width = input->width();
@@ -41,21 +63,57 @@ static SkImage* flipSkImageVertically(SkImage* input)
     return SkImage::NewRasterCopy(info, imagePixels.get(), imageRowBytes);
 }
 
-static PassRefPtr<StaticBitmapImage> cropImage(Image* image, const IntRect& cropRect, bool flipYEnabled)
+// TODO(xidachen): the part of read an SkImage to a OwnPtr<uint8_t[]> has been used in multiple places,
+// we should write it as a utility function here.
+static SkImage* premulSkImageToUnPremul(SkImage* input)
+{
+    int width = input->width();
+    int height = input->height();
+    SkImageInfo info = SkImageInfo::Make(width, height, kN32_SkColorType, kUnpremul_SkAlphaType);
+    OwnPtr<uint8_t[]> dstPixels = adoptArrayPtr(new uint8_t[width * height * info.bytesPerPixel()]);
+    size_t dstRowBytes = info.bytesPerPixel() * width;
+    input->readPixels(info, dstPixels.get(), dstRowBytes, 0, 0);
+    return SkImage::NewRasterCopy(info, dstPixels.get(), dstRowBytes);
+}
+
+static PassRefPtr<StaticBitmapImage> cropImage(Image* image, const IntRect& cropRect, bool flipYEnabled, bool premultiplyAlphaEnabled)
 {
     ASSERT(image);
 
     IntRect imgRect(IntPoint(), IntSize(image->width(), image->height()));
     const IntRect srcRect = intersection(imgRect, cropRect);
 
+    RefPtr<SkImage> skiaImage = image->imageForCurrentFrame();
+    // Attempt to get raw unpremultiplied image data.
+    if (((!premultiplyAlphaEnabled && !skiaImage->isOpaque()) || !skiaImage) && image->data()) {
+        // TODO(xidachen): GammaAndColorProfileApplied needs to be changed when working on color-space conversion
+        OwnPtr<ImageDecoder> decoder(ImageDecoder::create(
+            *(image->data()), ImageDecoder::AlphaNotPremultiplied,
+            ImageDecoder::GammaAndColorProfileApplied));
+        if (!decoder)
+            return nullptr;
+        decoder->setData(image->data(), true);
+        if (!decoder->frameCount())
+            return nullptr;
+        ImageFrame* frame = decoder->frameBufferAtIndex(0);
+        if (!frame || frame->status() != ImageFrame::FrameComplete)
+            return nullptr;
+        SkBitmap bitmap = frame->bitmap();
+        if (!frameIsValid(bitmap))
+            return nullptr;
+        ASSERT(bitmap.isImmutable());
+        skiaImage = adoptRef(SkImage::NewFromBitmap(bitmap));
+    }
+
     if (cropRect == srcRect) {
         if (flipYEnabled)
-            return StaticBitmapImage::create(adoptRef(flipSkImageVertically(image->imageForCurrentFrame()->newSubset(srcRect))));
-        return StaticBitmapImage::create(adoptRef(image->imageForCurrentFrame()->newSubset(srcRect)));
+            return StaticBitmapImage::create(adoptRef(flipSkImageVertically(skiaImage->newSubset(srcRect))));
+        return StaticBitmapImage::create(adoptRef(skiaImage->newSubset(srcRect)));
     }
 
     RefPtr<SkSurface> surface = adoptRef(SkSurface::NewRasterN32Premul(cropRect.width(), cropRect.height()));
-
+    // In the case where cropRect doesn't intesect the source image, we return a premultiplied transparent black SkImage.
+    // If we decide we want to grab meta data from m_image, we have to change this.
     if (srcRect.isEmpty())
         return StaticBitmapImage::create(adoptRef(surface->newImageSnapshot()));
 
@@ -65,18 +123,23 @@ static PassRefPtr<StaticBitmapImage> cropImage(Image* image, const IntRect& crop
         dstLeft = -cropRect.x();
     if (cropRect.y() < 0)
         dstTop = -cropRect.y();
-    surface->getCanvas()->drawImage(image->imageForCurrentFrame().get(), dstLeft, dstTop);
+    surface->getCanvas()->drawImage(skiaImage.get(), dstLeft, dstTop);
     if (flipYEnabled)
-        return StaticBitmapImage::create(adoptRef(flipSkImageVertically(surface->newImageSnapshot())));
-    return StaticBitmapImage::create(adoptRef(surface->newImageSnapshot()));
+        skiaImage = adoptRef(flipSkImageVertically(surface->newImageSnapshot()));
+    else
+        skiaImage = adoptRef(surface->newImageSnapshot());
+    if (premultiplyAlphaEnabled)
+        return StaticBitmapImage::create(skiaImage);
+    return StaticBitmapImage::create(adoptRef(premulSkImageToUnPremul(skiaImage.get())));
 }
 
 ImageBitmap::ImageBitmap(HTMLImageElement* image, const IntRect& cropRect, Document* document, const ImageBitmapOptions& options)
 {
-    if (options.imageOrientation() == imageOrientationFlipY)
-        m_image = cropImage(image->cachedImage()->image(), cropRect, true);
-    else
-        m_image = cropImage(image->cachedImage()->image(), cropRect, false);
+    bool imageOrientationFlipYFlag;
+    bool premultiplyAlphaEnabledFlag;
+    parseOptions(options, imageOrientationFlipYFlag, premultiplyAlphaEnabledFlag);
+
+    m_image = cropImage(image->cachedImage()->image(), cropRect, imageOrientationFlipYFlag, premultiplyAlphaEnabledFlag);
     m_image->setOriginClean(!image->wouldTaintOrigin(document->securityOrigin()));
 }
 
@@ -104,10 +167,10 @@ ImageBitmap::ImageBitmap(HTMLVideoElement* video, const IntRect& cropRect, Docum
 ImageBitmap::ImageBitmap(HTMLCanvasElement* canvas, const IntRect& cropRect, const ImageBitmapOptions& options)
 {
     ASSERT(canvas->isPaintable());
-    if (options.imageOrientation() == imageOrientationFlipY)
-        m_image = cropImage(canvas->copiedImage(BackBuffer, PreferAcceleration).get(), cropRect, true);
-    else
-        m_image = cropImage(canvas->copiedImage(BackBuffer, PreferAcceleration).get(), cropRect, false);
+    bool imageOrientationFlipYFlag;
+    bool premultiplyAlphaEnabledFlag;
+    parseOptions(options, imageOrientationFlipYFlag, premultiplyAlphaEnabledFlag);
+    m_image = cropImage(canvas->copiedImage(BackBuffer, PreferAcceleration).get(), cropRect, imageOrientationFlipYFlag, premultiplyAlphaEnabledFlag);
     m_image->setOriginClean(canvas->originClean());
 }
 
@@ -138,19 +201,19 @@ ImageBitmap::ImageBitmap(ImageData* data, const IntRect& cropRect, const ImageBi
 
 ImageBitmap::ImageBitmap(ImageBitmap* bitmap, const IntRect& cropRect, const ImageBitmapOptions& options)
 {
-    if (options.imageOrientation() == imageOrientationFlipY)
-        m_image = cropImage(bitmap->bitmapImage(), cropRect, true);
-    else
-        m_image = cropImage(bitmap->bitmapImage(), cropRect, false);
+    bool imageOrientationFlipYFlag;
+    bool premultiplyAlphaEnabledFlag;
+    parseOptions(options, imageOrientationFlipYFlag, premultiplyAlphaEnabledFlag);
+    m_image = cropImage(bitmap->bitmapImage(), cropRect, imageOrientationFlipYFlag, true);
     m_image->setOriginClean(bitmap->originClean());
 }
 
 ImageBitmap::ImageBitmap(PassRefPtr<StaticBitmapImage> image, const IntRect& cropRect, const ImageBitmapOptions& options)
 {
-    if (options.imageOrientation() == imageOrientationFlipY)
-        m_image = cropImage(image.get(), cropRect, true);
-    else
-        m_image = cropImage(image.get(), cropRect, false);
+    bool imageOrientationFlipYFlag;
+    bool premultiplyAlphaEnabledFlag;
+    parseOptions(options, imageOrientationFlipYFlag, premultiplyAlphaEnabledFlag);
+    m_image = cropImage(image.get(), cropRect, imageOrientationFlipYFlag, premultiplyAlphaEnabledFlag);
     m_image->setOriginClean(image->originClean());
 }