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 c10d390f56f61396fa2ddbb55d35ab70637f577c..bc9bdea65fafd21292c1153f9fd40c70bde96c6e 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 +284,10 @@ private:
 
 /////////////////////////////////////////////////////////////////////////////
 
+static SkPaint* set_if_needed(SkLazyPaint* lazy, const SkPaint& orig) {
+    return lazy->isValid() ? lazy->get() : lazy->set(orig);
+}
+
 class AutoDrawLooper {
 public:
     AutoDrawLooper(SkCanvas* canvas, const SkSurfaceProps& props, const SkPaint& paint,
@@ -295,9 +300,23 @@ public:
         fDoClearImageFilter = false;
         fDone = false;
 
-        if (!skipLayerForImageFilter && fOrigPaint.getImageFilter()) {
+        // Transform imagefilter into colorfilter?
+        if (fOrigPaint.getImageFilter()) {
+            SkColorFilter* embeddedCF = NULL;
+            SkColorFilter* paintCF = fOrigPaint.getColorFilter();
+            // When we fix http://code.google.com/p/skia/issues/detail?id=3479 we can support
+            // composing paintCF w/ embeddedCF.
+            if (NULL == paintCF && fOrigPaint.getImageFilter()->asColorFilter(&embeddedCF)) {

[Stephen White, 2015/03/02 18:50:22]

Need to check for !getInput(0) here?

[reed2, 2015/03/08 21:39:45]

asAColorFilter takes care of that check.

+                SkPaint* paint = set_if_needed(&fLazyPaintInit, fOrigPaint);
+                paint->setColorFilter(embeddedCF)->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 +338,7 @@ 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 +369,7 @@ public:
     }
 
 private:
-    SkLazyPaint     fLazyPaint;
+    SkLazyPaint     fLazyPaintInit, fLazyPaintPerNext;
     SkCanvas*       fCanvas;
     const SkPaint&  fOrigPaint;
     SkDrawFilter*   fFilter;
@@ -371,7 +390,7 @@ 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) {