Implement a generic matrix transform image filter.

gm/matriximagefilter.cpp

Index: gm/matriximagefilter.cpp
diff --git a/gm/matriximagefilter.cpp b/gm/matriximagefilter.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..ac8b94f148402d568773533a6e93c2d72f62e6be
--- /dev/null
+++ b/gm/matriximagefilter.cpp
@@ -0,0 +1,97 @@
+/*
+ * 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 "SkMatrixImageFilter.h"
+
+namespace skiagm {
+
+class MatrixImageFilterGM : public GM {
+public:
+    MatrixImageFilterGM() {
+        this->setBGColor(0x00000000);
+    }
+
+protected:
+    virtual SkString onShortName() {
+        return SkString("matriximagefilter");
+    }
+
+    void draw(SkCanvas* canvas, const SkRect& rect, const SkBitmap& bitmap,
+              const SkMatrix& matrix, SkPaint::FilterLevel filterLevel) {
+        SkAutoTUnref<SkImageFilter> imageFilter(
+            SkMatrixImageFilter::Create(matrix, filterLevel));
+        SkPaint paint;
+        paint.setImageFilter(imageFilter.get());
+        canvas->saveLayer(&rect, &paint);
+        canvas->drawBitmap(bitmap, 0, 0);
+        canvas->restore();
+    }
+
+    virtual SkISize onISize() {
+        return make_isize(420, 100);
+    }
+
+    void make_checkerboard(SkBitmap* bitmap) {
+        bitmap->allocN32Pixels(64, 64);
+        SkCanvas canvas(*bitmap);
+        SkPaint darkPaint;
+        darkPaint.setColor(0xFF404040);
+        SkPaint lightPaint;
+        lightPaint.setColor(0xFFA0A0A0);
+        for (int y = 0; y < 64; y += 32) {
+            for (int x = 0; x < 64; x += 32) {
+                canvas.save();
+                canvas.translate(SkIntToScalar(x), SkIntToScalar(y));
+                canvas.drawRect(SkRect::MakeXYWH(0, 0, 16, 16), darkPaint);
+                canvas.drawRect(SkRect::MakeXYWH(16, 0, 16, 16), lightPaint);
+                canvas.drawRect(SkRect::MakeXYWH(0, 16, 16, 16), lightPaint);
+                canvas.drawRect(SkRect::MakeXYWH(16, 16, 16, 16), darkPaint);
+                canvas.restore();
+            }
+        }
+    }
+
+    virtual void onDraw(SkCanvas* canvas) {
+        canvas->clear(0x00000000);
+        SkPaint paint;
+        SkMatrix matrix;
+        SkScalar margin = SkIntToScalar(10);
+        matrix.setSkew(SkDoubleToScalar(0.5), SkDoubleToScalar(0.2));
+        SkRect srcBounds;
+        SkBitmap checkerboard;
+        make_checkerboard(&checkerboard);
+        checkerboard.getBounds(&srcBounds);
+        // Outer paint does no filtering; leave it all for the filter
+        paint.setFilterLevel(SkPaint::kNone_FilterLevel);
+
+        SkRect srcRect = SkRect::MakeWH(96, 96);
+
+        canvas->translate(margin, margin);
+        draw(canvas, srcRect, checkerboard, matrix, SkPaint::kNone_FilterLevel);
+
+        canvas->translate(srcRect.width() + margin, 0);
+        draw(canvas, srcRect, checkerboard, matrix, SkPaint::kLow_FilterLevel);
+
+        canvas->translate(srcRect.width() + margin, 0);
+        draw(canvas, srcRect, checkerboard, matrix, SkPaint::kMedium_FilterLevel);
+
+        canvas->translate(srcRect.width() + margin, 0);
+        draw(canvas, srcRect, checkerboard, matrix, SkPaint::kHigh_FilterLevel);
+    }
+
+private:
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static GM* MyFactory(void*) { return new MatrixImageFilterGM; }
+static GMRegistry reg(MyFactory);
+
+}