JPEGImageDecoder RGB565 and downsample support and related Skia imagegenerator changes

third_party/WebKit/Source/platform/image-decoders/ImageFrame.h

Index: third_party/WebKit/Source/platform/image-decoders/ImageFrame.h
diff --git a/third_party/WebKit/Source/platform/image-decoders/ImageFrame.h b/third_party/WebKit/Source/platform/image-decoders/ImageFrame.h
index fb7425755bd77887066531b171c6c8dc21c5b2d8..fa01521e116ff0e65fc1beb8b0b43a43f448b4b7 100644
--- a/third_party/WebKit/Source/platform/image-decoders/ImageFrame.h
+++ b/third_party/WebKit/Source/platform/image-decoders/ImageFrame.h
@@ -66,7 +66,14 @@ public:
         // overwrite the corresponding pixels).
         BlendAtopBgcolor,
     };
+
+    enum ColorType {
+        RGBA8888 = kRGBA_8888_SkColorType,
+        RGB565 = kRGB_565_SkColorType
+    };
+
     typedef uint32_t PixelData;
+    typedef uint16_t PixelData16;
 
     ImageFrame();
 
@@ -109,7 +116,8 @@ public:
     // Allocates space for the pixel data.  Must be called before any pixels
     // are written.  Must only be called once.  Returns whether allocation
     // succeeded.
-    bool setSize(int newWidth, int newHeight);
+    // called from decoder before start writing pixel data

[scroggo_chromium, 2015/10/19 20:41:36]

I don't see how this says anything different from "Must be called before any
pixels are written", above.

[aleksandar.stojiljkovic, 2015/10/20 09:51:12]

Updating it, "Must only be called once" is not needed.
My intention was to document usage in current code - that it is called from
decoder.

+    bool setSize(int newWidth, int newHeight, ColorType bitmapType = RGBA8888);
 
     // Returns a caller-owned pointer to the underlying native image data.
     // (Actual use: This pointer will be owned by BitmapImage and freed in
@@ -146,6 +154,12 @@ public:
         return m_bitmap.getAddr32(x, y);
     }
 
+    template<class T>
+    inline T* getAddrT(int x, int y)
+    {
+        ASSERT_NOT_REACHED();
+    }
+
     inline void setRGBA(int x, int y, unsigned r, unsigned g, unsigned b, unsigned a)
     {
         setRGBA(getAddr(x, y), r, g, b, a);
@@ -178,6 +192,11 @@ public:
         *dest = SkPackARGB32NoCheck(a, r, g, b);
     }
 
+    static inline void setRGB565(PixelData16* dest, unsigned r, unsigned g, unsigned b)
+    {
+        *dest = SkDitherPack888ToRGB16(r, g, b);

[aleksandar.stojiljkovic, 2015/10/19 18:17:09]

Dither: Don't know if it makes sense to use ordered dithering here.
Floyd-Steinberg was set for all decoding (so this too).
For clarification, this path is executed when there is color profile (e.g. when
QCMS is in use and then output is set to rgb), so when output is RGB or CMYK.

This path is not executed when jpeg output is JCS_RGB565 - scanlines are
directly outputted to SkBitmap's rows.

+    }
+
     // Notifies the SkBitmap if any pixels changed and resets the flag.
     inline void notifyBitmapIfPixelsChanged()
     {
@@ -218,6 +237,18 @@ private:
     size_t m_requiredPreviousFrameIndex;
 };
 
+template<>
+inline ImageFrame::PixelData* ImageFrame::getAddrT<ImageFrame::PixelData>(int x, int y)
+{
+    return m_bitmap.getAddr32(x, y);
+}
+
+template<>
+inline ImageFrame::PixelData16* ImageFrame::getAddrT<ImageFrame::PixelData16>(int x, int y)
+{
+    return m_bitmap.getAddr16(x, y);
+}
+
 } // namespace blink
 
 #endif