Implement InterpolationMedium to filter animated images

Source/core/rendering/ImageQualityController.cpp

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 42 matching lines @@
 {
     if (gImageQualityController) {
         gImageQualityController->objectDestroyed(renderer);
         if (gImageQualityController->isEmpty()) {
             delete gImageQualityController;
             gImageQualityController = 0;
         }
     }
 }
 
+InterpolationQuality ImageQualityController::chooseInterpolationQuality(GraphicsContext* context, RenderObject* object, Image* image, const void* layer, const LayoutSize& layoutSize)
+{
+    if (shouldPaintAtLowQuality(context, object, image, layer, layoutSize))
+        return InterpolationLow;

[Stephen White, 2014/03/18 17:26:43]

We actually might want to consider using Medium here as well, to get mips for
minification on animated HTML elements as well. But we can consider that in a
separate change.

[Alpha Left Google, 2014/03/18 22:59:13]

That's right. We can update that later.

+
+    // For images that are potentially animated we paint them at low quality.

[Stephen Chennney, 2014/03/18 12:56:32]

This comment doesn't seem to match the code. Is the problem the comment or the
semantics of InterpolationMedium.

[Alpha Left Google, 2014/03/18 22:59:13]

The code is correct. I've updated the comments.

+    if (image && image->maybeAnimated())
+        return InterpolationMedium;
+
+    return InterpolationDefault;
+}
+
 ImageQualityController::~ImageQualityController()
 {
     // This will catch users of ImageQualityController that forget to call cleanUp.
     ASSERT(!gImageQualityController || gImageQualityController->isEmpty());
 }
 
 ImageQualityController::ImageQualityController()
     : m_timer(this, &ImageQualityController::highQualityRepaintTimerFired)
     , m_animatedResizeIsActive(false)
     , m_liveResizeOptimizationIsActive(false)
@@ skipping 57 matching lines @@
 bool ImageQualityController::shouldPaintAtLowQuality(GraphicsContext* context, RenderObject* object, Image* image, const void *layer, const LayoutSize& layoutSize)
 {
     // If the image is not a bitmap image, then none of this is relevant and we just paint at high
     // quality.
     if (!image || !image->isBitmapImage() || context->paintingDisabled())
         return false;
 
     if (object->style()->imageRendering() == ImageRenderingOptimizeContrast)
         return true;
 
-    // For images that are potentially animated we paint them at low quality.
-    if (image->maybeAnimated())
-        return true;
-
     // Look ourselves up in the hashtables.
     ObjectLayerSizeMap::iterator i = m_objectLayerSizeMap.find(object);
     LayerSizeMap* innerMap = i != m_objectLayerSizeMap.end() ? &i->value : 0;
     LayoutSize oldSize;
     bool isFirstResize = true;
     if (innerMap) {
         LayerSizeMap::iterator j = innerMap->find(layer);
         if (j != innerMap->end()) {
             isFirstResize = false;
             oldSize = j->value;
@@ skipping 53 matching lines @@
     // This object has been resized to two different sizes while the timer
     // is active, so draw at low quality, set the flag for animated resizes and
     // the object to the list for high quality redraw.
     set(object, innerMap, layer, scaledLayoutSize);
     m_animatedResizeIsActive = true;
     restartTimer();
     return true;
 }
 
 } // namespace WebCore