alpha threshold bitmap shader

gm/bitmapalphathreshold.cpp

Index: gm/bitmapalphathreshold.cpp
diff --git a/gm/bitmapalphathreshold.cpp b/gm/bitmapalphathreshold.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..8af49fe351ea69a2b7133224f2d3a71602639938
--- /dev/null
+++ b/gm/bitmapalphathreshold.cpp
@@ -0,0 +1,144 @@
+/*
+ * Copyright 2013 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 "SkGradientShader.h"
+#include "SkBitmapAlphaThresholdShader.h"
+#include "SkTArray.h"
+#include "SkParsePath.h"
+
+class BitmapAlphaThresholdGM : public skiagm::GM {
+public:
+    BitmapAlphaThresholdGM() {
+        this->setBGColor(0xFF000000);
+    }
+
+private:
+    virtual uint32_t onGetFlags() const SK_OVERRIDE {
+        // narrow this flags when the shader has a CPU implementation and
+        // when it serializes.
+        return 
+            kSkipPDF_Flag               |
+            kSkipPicture_Flag           |
+            kSkipPipe_Flag              |
+            kSkipPipeCrossProcess_Flag  |
+            kSkipTiled_Flag             |
+            kSkip565_Flag               |
+            kSkipScaledReplay_Flag      |
+            kSkipPDFRasterization_Flag  |
+
+            kGPUOnly_Flag;
+    }
+
+    virtual void onOnceBeforeDraw() SK_OVERRIDE {
+        fBM.setConfig(SkBitmap::kARGB_8888_Config, 100, 100);
+        if (!fBM.allocPixels()) {
+            return;
+        }
+        SkCanvas canvas(fBM);
+        SkPoint pts[] = { {0, 0}, {SkIntToScalar(fBM.width()), SkIntToScalar(fBM.height())} };
+        SkColor colors[] = {0x00000000, 0xffffffff};
+        SkShader* grad = SkGradientShader::CreateLinear(pts, colors, NULL, 2,
+                                                        SkShader::kClamp_TileMode);
+        SkPaint gradPaint;
+        gradPaint.setShader(grad)->unref();
+        gradPaint.setXfermodeMode(SkXfermode::kSrc_Mode);
+        canvas.drawPaint(gradPaint);
+
+        // Construct the region used as a mask.
+        SkRegion bmpBoundsClip;
+        bmpBoundsClip.setRect(0, 0, fBM.width(), fBM.height());
+        SkPath circlePath;
+        SkScalar radius = SkScalarSqrt(SkIntToScalar(fBM.width() * fBM.height())) / 2;
+        circlePath.addCircle(SkIntToScalar(fBM.width() / 2),
+                             SkIntToScalar(fBM.height() / 2),
+                             radius);
+        fMask.setPath(circlePath, bmpBoundsClip);
+
+        SkPath batPath;
+        SkParsePath::FromSVGString(
+        "M305.214,374.779c2.463,0,3.45,0.493,3.45,0.493l1.478-6.241c0,0,1.15,4.763,1.643,9.034"
+		"c0.493,4.271,8.048,1.479,14.454,0.164c6.405-1.314,7.72-11.662,7.72-11.662h59.294c0,0-35.807,10.841-26.772,34.656"
+		"c0,0-52.889-8.048-61.101,24.967h-0.001c-8.212-33.015-61.101-24.967-61.101-24.967c9.034-23.815-26.772-34.656-26.772-34.656"
+		"h59.294c0,0,1.314,10.348,7.719,11.662c6.406,1.314,13.962,4.106,14.454-0.164c0.493-4.271,1.643-9.034,1.643-9.034l1.479,6.241"
+		"c0,0,0.985-0.493,3.449-0.493H305.214L305.214,374.779z",
+        &batPath);
+
+        SkMatrix matrix;
+        matrix.setTranslate(-208, -280);
+        matrix.postScale(radius / 100, radius / 100);
+        batPath.transform(matrix, &batPath);
+        SkRegion batRegion;
+        batRegion.setPath(batPath, bmpBoundsClip);
+
+        fMask.op(batRegion, SkRegion::kDifference_Op);
+    }
+
+    virtual SkString onShortName() SK_OVERRIDE {
+        return SkString("bat");
+    }
+
+    virtual SkISize onISize() SK_OVERRIDE {
+        return SkISize::Make(518, 735);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+
+        SkTArray<SkMatrix> lms;
+        lms.push_back().reset();
+        lms.push_back().setScale(SK_Scalar1 / 2, SK_Scalar1);
+        lms.push_back().setScale(SK_Scalar1, 2 * SK_Scalar1);
+        lms.push_back().setRotate(-SK_Scalar1 * 30);
+        lms.push_back().setSkew(0, SK_Scalar1 / 5);
+
+        static const SkScalar kMargin = 5 * SK_Scalar1;
+        canvas->translate(kMargin, kMargin);
+        canvas->save();
+
+        static const U8CPU kThresholds[] = { 0x0, 0x08, 0x40, 0x80, 0xC0, 0xF0, 0xFF };
+
+        for (size_t i = 0; i < SK_ARRAY_COUNT(kThresholds); ++i) {
+            for (int j = 0; j < lms.count(); ++j) {
+                SkRect rect;
+                rect.fLeft = 0;
+                rect.fTop = 0;
+                rect.fRight = SkIntToScalar(fBM.width());
+                rect.fBottom = SkIntToScalar(fBM.height());
+
+                SkShader* thresh;
+                // This SkShader currently only has a GPU implementation.
+                if (canvas->getDevice()->accessRenderTarget()) {
+                    thresh = SkBitmapAlphaThresholdShader::Create(fBM, fMask, kThresholds[i]);
+                } else {
+                    thresh = SkShader::CreateBitmapShader(fBM, SkShader::kClamp_TileMode,
+                                                               SkShader::kClamp_TileMode);
+                }
+
+                thresh->setLocalMatrix(lms[j]);
+
+                SkPaint paint;
+                paint.setShader(thresh)->unref();
+
+                canvas->drawRect(rect, paint);
+                canvas->translate(SkIntToScalar(fBM.width() + kMargin), 0);
+            }
+            canvas->restore();
+            canvas->translate(0, SkIntToScalar(fBM.height() + kMargin));
+            canvas->save();
+        }
+
+    }
+
+    SkBitmap    fBM;
+    SkRegion    fMask;
+
+    typedef skiagm::GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM( return new BitmapAlphaThresholdGM(); )