SkBlurImageFilter returns input when sigma = 0

In the current implementation, a blur filter is always created even in the
case when sigma.fX == 0 && sigma.fY == 0. This CL makes the blur filter
return input in this case.

BUG=568393

Review URL: https://codereview.chromium.org/1518643002

6 files changed, 18 insertions, 10 deletions

diff --git a/bench/BlurImageFilterBench.cpp b/bench/BlurImageFilterBench.cpp
index 7ed600632a..f0a7a8eea0 100644
--- a/bench/BlurImageFilterBench.cpp
+++ b/bench/BlurImageFilterBench.cpp
@@ -80,7 +80,8 @@ protected:
 
         const SkImageFilter::CropRect* crop =
             fIsExpanded ? &cropRectLarge : fIsCropped ? &cropRect : nullptr;
-        paint.setImageFilter(SkBlurImageFilter::Create(fSigmaX, fSigmaY, input, crop))->unref();
+        SkAutoTUnref<SkImageFilter> blur(SkBlurImageFilter::Create(fSigmaX, fSigmaY, input, crop));
+        paint.setImageFilter(blur);
 
         for (int i = 0; i < loops; i++) {
             canvas->drawBitmap(fCheckerboard, kX, kY, &paint);
diff --git a/gm/imageblur.cpp b/gm/imageblur.cpp
index 575f02c095..22ea408e27 100644
--- a/gm/imageblur.cpp
+++ b/gm/imageblur.cpp
@@ -14,7 +14,8 @@
 
 void imageblurgm_draw(SkScalar fSigmaX, SkScalar fSigmaY, SkCanvas* canvas) {
         SkPaint paint;
-        paint.setImageFilter(SkBlurImageFilter::Create(fSigmaX, fSigmaY))->unref();
+        SkAutoTUnref<SkImageFilter> blur(SkBlurImageFilter::Create(fSigmaX, fSigmaY));
+        paint.setImageFilter(blur);
         canvas->saveLayer(nullptr, &paint);
         const char* str = "The quick brown fox jumped over the lazy dog.";
 
diff --git a/gm/imageblur2.cpp b/gm/imageblur2.cpp
index 223582f120..2b95c02ab1 100644
--- a/gm/imageblur2.cpp
+++ b/gm/imageblur2.cpp
@@ -58,7 +58,8 @@ protected:
                 SkScalar sigmaY = kBlurSigmas[y];
 
                 SkPaint paint;
-                paint.setImageFilter(SkBlurImageFilter::Create(sigmaX, sigmaY))->unref();
+                SkAutoTUnref<SkImageFilter> blur(SkBlurImageFilter::Create(sigmaX, sigmaY));
+                paint.setImageFilter(blur);
                 canvas->saveLayer(nullptr, &paint);
 
                 SkRandom rand;
diff --git a/gm/imageblurtiled.cpp b/gm/imageblurtiled.cpp
index 68e5785ddf..9f8bfe510f 100644
--- a/gm/imageblurtiled.cpp
+++ b/gm/imageblurtiled.cpp
@@ -31,7 +31,8 @@ protected:
 
     virtual void onDraw(SkCanvas* canvas) {
         SkPaint paint;
-        paint.setImageFilter(SkBlurImageFilter::Create(fSigmaX, fSigmaY))->unref();
+        SkAutoTUnref<SkImageFilter> blur(SkBlurImageFilter::Create(fSigmaX, fSigmaY));
+        paint.setImageFilter(blur);
         const SkScalar tile_size = SkIntToScalar(128);
         SkRect bounds;
         if (!canvas->getClipBounds(&bounds)) {
diff --git a/gm/imagefilters.cpp b/gm/imagefilters.cpp
index af2c776ce1..5f1ae84949 100644
--- a/gm/imagefilters.cpp
+++ b/gm/imagefilters.cpp
@@ -22,7 +22,7 @@
 static void do_draw(SkCanvas* canvas, SkXfermode::Mode mode, SkImageFilter* imf) {
         SkAutoCanvasRestore acr(canvas, true);
         canvas->clipRect(SkRect::MakeWH(220, 220));
-        
+
         // want to force a layer, so modes like DstIn can combine meaningfully, but the final
         // image can still be shown against our default (opaque) background. non-opaque GMs
         // are a lot more trouble to compare/triage.
@@ -31,10 +31,10 @@ static void do_draw(SkCanvas* canvas, SkXfermode::Mode mode, SkImageFilter* imf)
 
         SkPaint paint;
         paint.setAntiAlias(true);
-        
+
         SkRect r0 = SkRect::MakeXYWH(10, 60, 200, 100);
         SkRect r1 = SkRect::MakeXYWH(60, 10, 100, 200);
-        
+
         paint.setColor(SK_ColorRED);
         canvas->drawOval(r0, paint);
 
@@ -54,14 +54,14 @@ DEF_SIMPLE_GM(imagefilters_xfermodes, canvas, 480, 480) {
         const SkXfermode::Mode modes[] = {
             SkXfermode::kSrcATop_Mode, SkXfermode::kDstIn_Mode
         };
-        
+
         for (size_t i = 0; i < SK_ARRAY_COUNT(modes); ++i) {
             canvas->save();
             do_draw(canvas, modes[i], nullptr);
             canvas->translate(240, 0);
             do_draw(canvas, modes[i], imf);
             canvas->restore();
-            
+
             canvas->translate(0, 240);
         }
 }
@@ -87,7 +87,8 @@ DEF_SIMPLE_GM(fast_slow_blurimagefilter, canvas, 620, 260) {
     canvas->translate(10, 10);
     for (SkScalar sigma = 8; sigma <= 128; sigma *= 2) {
         SkPaint paint;
-        paint.setImageFilter(SkBlurImageFilter::Create(sigma, sigma))->unref();
+        SkAutoTUnref<SkImageFilter> blur(SkBlurImageFilter::Create(sigma, sigma));
+        paint.setImageFilter(blur);
 
         canvas->save();
         // we outset the clip by 1, to fall out of the fast-case in drawImage
diff --git a/include/effects/SkBlurImageFilter.h b/include/effects/SkBlurImageFilter.h
index 7f62634a9e..5ae013d78e 100644
--- a/include/effects/SkBlurImageFilter.h
+++ b/include/effects/SkBlurImageFilter.h
@@ -15,6 +15,9 @@ class SK_API SkBlurImageFilter : public SkImageFilter {
 public:
     static SkImageFilter* Create(SkScalar sigmaX, SkScalar sigmaY, SkImageFilter* input = NULL,
                                  const CropRect* cropRect = NULL) {
+        if (0 == sigmaX && 0 == sigmaY && nullptr == cropRect) {
+            return SkSafeRef(input);
+        }
         return new SkBlurImageFilter(sigmaX, sigmaY, input, cropRect);
     }