Add a new GM to show problems with shear/rotate CTM w/ image filters.

gm/imagefilterstransformed.cpp

Index: gm/imagefilterstransformed.cpp
diff --git a/gm/imagefilterstransformed.cpp b/gm/imagefilterstransformed.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..f21a5ce70250bee1c5fac4a896c480195e084551
--- /dev/null
+++ b/gm/imagefilterstransformed.cpp
@@ -0,0 +1,125 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "sk_tool_utils.h"
+#include "SkBitmapSource.h"
+#include "SkBlurImageFilter.h"
+#include "SkColor.h"
+#include "SkDisplacementMapEffect.h"
+#include "SkDropShadowImageFilter.h"
+#include "SkGradientShader.h"
+#include "SkMorphologyImageFilter.h"
+#include "SkScalar.h"
+#include "gm.h"
+
+namespace skiagm {
+
+// This GM draws image filters with a CTM containing shearing / rotation.
+// It checks that the scale portion of the CTM is correctly extracted
+// and applied to the image inputs separately from the non-scale portion.
+
+class ImageFiltersTransformedGM : public GM {
+public:
+    ImageFiltersTransformedGM() {
+        this->setBGColor(SK_ColorBLACK);
+    }
+
+protected:
+
+    SkString onShortName() SK_OVERRIDE { return SkString("imagefilterstransformed"); }
+
+    SkISize onISize() SK_OVERRIDE { return SkISize::Make(420, 240); }
+
+    void makeGradientCircle(int width, int height) {
+        SkScalar x = SkIntToScalar(width / 2);
+        SkScalar y = SkIntToScalar(height / 2);
+        SkScalar radius = SkMinScalar(x, y) * 0.8f;
+        fGradientCircle.allocN32Pixels(width, height);
+        SkCanvas canvas(fGradientCircle);
+        canvas.clear(0x00000000);
+        SkColor colors[2];
+        colors[0] = SK_ColorWHITE;
+        colors[1] = SK_ColorBLACK;
+        SkAutoTUnref<SkShader> shader(
+            SkGradientShader::CreateRadial(SkPoint::Make(x, y), radius, colors, NULL, 2,
+                                           SkShader::kClamp_TileMode)
+        );
+        SkPaint paint;
+        paint.setShader(shader);
+        canvas.drawCircle(x, y, radius, paint);
+    }
+
+    void onOnceBeforeDraw() SK_OVERRIDE {
+        fCheckerboard.allocN32Pixels(64, 64);
+        SkCanvas checkerboardCanvas(fCheckerboard);
+        sk_tool_utils::draw_checkerboard(&checkerboardCanvas, 0xFFA0A0A0, 0xFF404040, 8);
+
+        this->makeGradientCircle(64, 64);
+    }
+
+    void onDraw(SkCanvas* canvas) SK_OVERRIDE {

[robertphillips, 2015/03/20 14:35:40]

Is this necessary - given the setting of the background color in the ctor?

+        canvas->clear(SK_ColorBLACK);
+
+        SkAutoTUnref<SkImageFilter> gradient(SkBitmapSource::Create(fGradientCircle));
+        SkAutoTUnref<SkImageFilter> checkerboard(SkBitmapSource::Create(fCheckerboard));
+        SkImageFilter* filters[] = {
+            SkBlurImageFilter::Create(12, 0),
+            SkDropShadowImageFilter::Create(0, 15, 8, 0, SK_ColorGREEN,
+                SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode),
+            SkDisplacementMapEffect::Create(SkDisplacementMapEffect::kR_ChannelSelectorType,
+                                            SkDisplacementMapEffect::kR_ChannelSelectorType,
+                                            12,
+                                            gradient.get(),
+                                            checkerboard.get()),
+            SkDilateImageFilter::Create(2, 2, checkerboard.get()),
+            SkErodeImageFilter::Create(2, 2, checkerboard.get()),
+        };
+
+        const SkScalar margin = SkIntToScalar(20);
+        const SkScalar size = SkIntToScalar(60);
+
+        for (size_t j = 0; j < 3; j++) {
+            canvas->save();
+            canvas->translate(margin, 0);
+            for (size_t i = 0; i < SK_ARRAY_COUNT(filters); ++i) {
+                SkPaint paint;
+                paint.setColor(SK_ColorWHITE);
+                paint.setImageFilter(filters[i]);
+                paint.setAntiAlias(true);
+                canvas->save();
+                canvas->translate(size * 0.5, size * 0.5);
+                canvas->scale(0.8, 0.8);
+                if (j == 1) {
+                    canvas->rotate(SkIntToScalar(45));
+                } else if (j == 2) {
+                    canvas->skew(0.5, 0.2);
+                }
+                canvas->translate(-size * 0.5, -size * 0.5);
+                canvas->drawOval(SkRect::MakeXYWH(0, size * 0.1, size, size * 0.6), paint);
+                canvas->restore();
+                canvas->translate(size + margin, 0);
+            }
+            canvas->restore();
+            canvas->translate(0, size + margin);
+        }
+
+        for (size_t i = 0; i < SK_ARRAY_COUNT(filters); ++i) {
+            SkSafeUnref(filters[i]);
+        }
+    }
+
+private:
+    SkBitmap fCheckerboard;
+    SkBitmap fGradientCircle;
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM( return new ImageFiltersTransformedGM; )
+
+}