use colorfilter instead of imagefilter when possible

src/core/SkCanvas.cpp

Index: src/core/SkCanvas.cpp
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index a47bd89c0507acad23ca7512279813ddd4a8697f..d80ad376f8b8484a62efc61700ed3b3846042731 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -8,6 +8,7 @@
 #include "SkCanvas.h"
 #include "SkCanvasPriv.h"
 #include "SkBitmapDevice.h"
+#include "SkColorFilter.h"
 #include "SkDeviceImageFilterProxy.h"
 #include "SkDraw.h"
 #include "SkDrawable.h"
@@ -283,6 +284,36 @@ private:
 
 /////////////////////////////////////////////////////////////////////////////
 
+static SkPaint* set_if_needed(SkLazyPaint* lazy, const SkPaint& orig) {
+    return lazy->isValid() ? lazy->get() : lazy->set(orig);
+}
+
+/**
+ *  If the paint has an imagefilter, but it can be simplified to just a colorfilter, return that
+ *  colorfilter, else return NULL.
+ */
+static SkColorFilter* image_to_color_filter(const SkPaint& paint) {
+    SkImageFilter* imgf = paint.getImageFilter();
+    if (!imgf) {
+        return NULL;
+    }
+
+    SkColorFilter* imgCF;
+    if (!imgf->asAColorFilter(&imgCF)) {
+        return NULL;
+    }
+
+    SkColorFilter* paintCF = paint.getColorFilter();
+    if (NULL == paintCF) {
+        // there is no existing paint colorfilter, so we can just return the imagefilter's
+        return imgCF;
+    }
+
+    // The paint has both a colorfilter and an imagefilter.
+    SkAutoTUnref<SkColorFilter> autoImgCF(imgCF);
+    return SkColorFilter::CreateComposeFilter(imgCF, paintCF);
+}
+
 class AutoDrawLooper {
 public:
     AutoDrawLooper(SkCanvas* canvas, const SkSurfaceProps& props, const SkPaint& paint,
@@ -295,9 +326,17 @@ public:
         fDoClearImageFilter = false;
         fDone = false;
 
-        if (!skipLayerForImageFilter && fOrigPaint.getImageFilter()) {
+        SkColorFilter* simplifiedCF = image_to_color_filter(fOrigPaint);
+        if (simplifiedCF) {
+            SkPaint* paint = set_if_needed(&fLazyPaintInit, fOrigPaint);
+            paint->setColorFilter(simplifiedCF)->unref();
+            paint->setImageFilter(NULL);
+            fPaint = paint;
+        }
+        
+        if (!skipLayerForImageFilter && fPaint->getImageFilter()) {
             SkPaint tmp;
-            tmp.setImageFilter(fOrigPaint.getImageFilter());
+            tmp.setImageFilter(fPaint->getImageFilter());
             (void)canvas->internalSaveLayer(bounds, &tmp, SkCanvas::kARGB_ClipLayer_SaveFlag,
                                             true, SkCanvas::kFullLayer_SaveLayerStrategy);
             // we'll clear the imageFilter for the actual draws in next(), so
@@ -319,7 +358,7 @@ public:
         uint32_t oldFlags = paint.getFlags();
         fNewPaintFlags = filter_paint_flags(props, oldFlags);
         if (fIsSimple && (fNewPaintFlags != oldFlags)) {
-            SkPaint* paint = fLazyPaint.set(fOrigPaint);
+            SkPaint* paint = set_if_needed(&fLazyPaintInit, fOrigPaint);
             paint->setFlags(fNewPaintFlags);
             fPaint = paint;
             // if we're not simple, doNext() will take care of calling setFlags()
@@ -350,7 +389,7 @@ public:
     }
 
 private:
-    SkLazyPaint     fLazyPaint;
+    SkLazyPaint     fLazyPaintInit, fLazyPaintPerNext;
     SkCanvas*       fCanvas;
     const SkPaint&  fOrigPaint;
     SkDrawFilter*   fFilter;
@@ -371,7 +410,8 @@ bool AutoDrawLooper::doNext(SkDrawFilter::Type drawType) {
     SkASSERT(!fIsSimple);
     SkASSERT(fLooperContext || fFilter || fDoClearImageFilter);
 
-    SkPaint* paint = fLazyPaint.set(fOrigPaint);
+    SkPaint* paint = fLazyPaintPerNext.set(fLazyPaintInit.isValid() ?
+                                           *fLazyPaintInit.get() : fOrigPaint);
     paint->setFlags(fNewPaintFlags);
 
     if (fDoClearImageFilter) {