Apply the CTM to filter parameters for 4 pixel-moving filters.

gm/imagefiltersscaled.cpp

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+#include "SkColor.h"
+#include "SkBitmapSource.h"
+#include "SkBlurImageFilter.h"
+#include "SkDisplacementMapEffect.h"
+#include "SkDropShadowImageFilter.h"
+#include "SkGradientShader.h"
+#include "SkScalar.h"
+
+namespace skiagm {
+
+class ImageFiltersScaledGM : public GM {
+public:
+    ImageFiltersScaledGM() : fInitialized(false) {
+        this->setBGColor(0x00000000);
+    }
+
+protected:
+    virtual SkString onShortName() {
+        return SkString("imagefiltersscaled");
+    }
+
+    virtual SkISize onISize() {
+        return make_isize(420, 100);
+    }
+
+    void make_checkerboard() {
+        fCheckerboard.setConfig(SkBitmap::kARGB_8888_Config, 80, 80);
+        fCheckerboard.allocPixels();
+        SkBitmapDevice device(fCheckerboard);
+        SkCanvas canvas(&device);
+        canvas.clear(0x00000000);
+        SkPaint darkPaint;
+        darkPaint.setColor(0xFF404040);
+        SkPaint lightPaint;
+        lightPaint.setColor(0xFFA0A0A0);
+        for (int y = 0; y < 80; y += 16) {
+          for (int x = 0; x < 80; x += 16) {
+            canvas.save();
+            canvas.translate(SkIntToScalar(x), SkIntToScalar(y));
+            canvas.drawRect(SkRect::MakeXYWH(0, 0, 8, 8), darkPaint);
+            canvas.drawRect(SkRect::MakeXYWH(8, 0, 8, 8), lightPaint);
+            canvas.drawRect(SkRect::MakeXYWH(0, 8, 8, 8), lightPaint);
+            canvas.drawRect(SkRect::MakeXYWH(8, 8, 8, 8), darkPaint);
+            canvas.restore();
+          }
+        }
+    }
+
+    void make_gradient_circle(int width, int height) {
+        SkScalar x = SkIntToScalar(width / 2);
+        SkScalar y = SkIntToScalar(height / 2);
+        SkScalar radius = SkScalarMul(SkMinScalar(x, y), SkIntToScalar(4) / SkIntToScalar(5));
+        fGradientCircle.setConfig(SkBitmap::kARGB_8888_Config, width, height);
+        fGradientCircle.allocPixels();
+        SkBitmapDevice device(fGradientCircle);
+        SkCanvas canvas(&device);
+        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);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) {
+        if (!fInitialized) {
+            this->make_checkerboard();
+            this->make_gradient_circle(64, 64);
+            fInitialized = true;
+        }
+        canvas->clear(0x00000000);
+
+        SkAutoTUnref<SkImageFilter> gradient(new SkBitmapSource(fGradientCircle));
+        SkAutoTUnref<SkImageFilter> checkerboard(new SkBitmapSource(fCheckerboard));
+
+        SkImageFilter* filters[] = {
+            NULL,
+            new SkBlurImageFilter(SkIntToScalar(4), SkIntToScalar(4)),
+            new SkDropShadowImageFilter(SkIntToScalar(5), SkIntToScalar(10), SkIntToScalar(3), SK_ColorYELLOW),
+            new SkDisplacementMapEffect(SkDisplacementMapEffect::kR_ChannelSelectorType,
+                                        SkDisplacementMapEffect::kR_ChannelSelectorType,
+                                        SkIntToScalar(12),
+                                        gradient.get(),
+                                        checkerboard.get()),
+        };
+
+        SkVector scales[] = {
+            SkVector::Make(SkIntToScalar(1), SkIntToScalar(1)),

[sugoi, 2014/01/17 21:56:27]

How about having at least 1 test case for downscaling (scale < 1) ?

[Stephen White, 2014/01/18 01:23:19]

Done.

+            SkVector::Make(SkIntToScalar(1), SkIntToScalar(3)),
+            SkVector::Make(SkIntToScalar(3), SkIntToScalar(1)),
+            SkVector::Make(SkIntToScalar(3), SkIntToScalar(3)),
+        };
+
+        SkRect r = SkRect::MakeWH(SkIntToScalar(64), SkIntToScalar(64));
+        SkScalar margin = SkIntToScalar(16);
+        SkRect bounds = r;
+        bounds.outset(margin, margin);
+
+        for (size_t j = 0; j < SK_ARRAY_COUNT(scales); ++j) {
+            canvas->save();
+            for (size_t i = 0; i < SK_ARRAY_COUNT(filters); ++i) {
+                SkPaint paint;
+                paint.setColor(SK_ColorBLUE);
+                paint.setImageFilter(filters[i]);
+                paint.setAntiAlias(true);
+                canvas->save();
+                canvas->scale(scales[j].fX, scales[j].fY);
+                canvas->clipRect(bounds);
+                canvas->drawCircle(r.centerX(), r.centerY(), SkScalarDiv(r.width()*2, SkIntToScalar(5)), paint);
+                canvas->restore();
+                canvas->translate(r.width() * scales[j].fX + margin, 0);
+            }
+            canvas->restore();
+            canvas->translate(0, r.height() * scales[j].fY + margin);
+        }
+    }
+
+private:
+    bool fInitialized;
+    SkBitmap fCheckerboard;
+    SkBitmap fGradientCircle;
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static GM* MyFactory(void*) { return new ImageFiltersScaledGM; }
+static GMRegistry reg(MyFactory);
+
+}