Change filter quality when scaling-down in drawImage

third_party/WebKit/Source/platform/graphics/Image.h

 /*
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2004, 2005, 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 10 matching lines @@
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef Image_h
 #define Image_h
 
 #include "platform/PlatformExport.h"
+#include "platform/geometry/FloatRect.h"
 #include "platform/geometry/IntRect.h"
 #include "platform/graphics/Color.h"
 #include "platform/graphics/GraphicsTypes.h"
 #include "platform/graphics/ImageAnimationPolicy.h"
 #include "platform/graphics/ImageObserver.h"
 #include "platform/graphics/ImageOrientation.h"
 #include "wtf/Assertions.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
@@ skipping 101 matching lines @@
 
     virtual void drawPattern(GraphicsContext&, const FloatRect&,
         const FloatSize&, const FloatPoint& phase, SkXfermode::Mode,
         const FloatRect&, const FloatSize& repeatSpacing = FloatSize());
 
     enum ImageClampingMode {
         ClampImageToSourceRect,
         DoNotClampImageToSourceRect
     };
 
-    virtual void draw(SkCanvas*, const SkPaint&, const FloatRect& dstRect, const FloatRect& srcRect, RespectImageOrientationEnum, ImageClampingMode) = 0;
+    virtual void draw(SkCanvas*, const SkPaint&, const FloatRect& dstRect, const FloatRect& srcRect, bool imageSmoothingEnabled, RespectImageOrientationEnum, ImageClampingMode) = 0;

[f(malita), 2016/07/18 15:46:38]

Instead of plumbing imageSmoothingEnabled in the Image API, why not adjust the
SkPaint filter quality before calling draw(...)?

[fs, 2016/07/18 15:56:55]

I was about to make a note about the same thing =). If it's about the
"adjusted*Rect"s being different, I don't think that's the case, since (IIRC)
the canvas code already clips the source rect and doesn't use image-orientation.

+    static bool isDrawScalingDown(const FloatRect& srcRect, const FloatRect& dstRect)
+    {
+        return dstRect.width() < srcRect.width() && dstRect.height() < srcRect.height();
+    }
 
     virtual bool applyShader(SkPaint&, const SkMatrix& localMatrix);
 
     // Compute the tile which contains a given point (assuming a repeating tile grid).
     // The point and returned value are in destination grid space.
     static FloatRect computeTileContaining(const FloatPoint&, const FloatSize& tileSize,
         const FloatPoint& tilePhase, const FloatSize& tileSpacing);
 
     // Compute the image subset which gets mapped onto dest, when the whole image is drawn into
     // tile.  Assumes the tile contains dest.  The tile rect is in destination grid space while
@@ skipping 18 matching lines @@
     UntracedMember<ImageObserver> m_imageObserver;
     bool m_imageObserverDisabled;
 };
 
 #define DEFINE_IMAGE_TYPE_CASTS(typeName) \
     DEFINE_TYPE_CASTS(typeName, Image, image, image->is##typeName(), image.is##typeName())
 
 } // namespace blink
 
 #endif