Added ComposeShaderBitmapGM that tests composing bitmaps with gradients

gm/composeshader.cpp

Index: gm/composeshader.cpp
diff --git a/gm/composeshader.cpp b/gm/composeshader.cpp
index f5ab996f37e33d332e50e37ef0e6ead58660aeaa..e012bbb28590b21282b59b47a3da5173c4e8603b 100644
--- a/gm/composeshader.cpp
+++ b/gm/composeshader.cpp
@@ -7,6 +7,7 @@
 
 #include "gm.h"
 
+#include "SkBitmapProcShader.h"
 #include "SkCanvas.h"
 #include "SkComposeShader.h"
 #include "SkGradientShader.h"
@@ -84,7 +85,7 @@ protected:
     }
 
     SkISize onISize() override {
-        return SkISize::Make(220, 750);
+        return SkISize::Make(750, 220);
     }
 
     void onDraw(SkCanvas* canvas) override {
@@ -115,9 +116,131 @@ protected:
             canvas->translate(0, r.height() + 5);
         }
     }
+
+private:
+    typedef GM INHERITED ;
+};
+
+
+// creates a square bitmap with red background and a green circle in the center
+static void draw_color_bm(SkBitmap* bm, int length) {
+    SkPaint paint;
+    paint.setColor(SK_ColorGREEN);
+
+    bm->allocN32Pixels(length, length);
+    bm->eraseColor(SK_ColorRED);
+
+    SkCanvas canvas(*bm);
+    canvas.drawCircle(SkIntToScalar(length/2), SkIntToScalar(length/2), SkIntToScalar(length/2),
+                      paint);
+}
+
+// creates a square alpha8 bitmap with transparent background and an opaque circle in the center
+static void draw_alpha8_bm(SkBitmap* bm, int length) {
+    SkPaint circlePaint;
+    circlePaint.setColor(SK_ColorBLACK);
+
+    bm->allocPixels(SkImageInfo::MakeA8(length, length));
+    bm->eraseColor(SK_ColorTRANSPARENT);
+
+    SkCanvas canvas(*bm);
+    canvas.drawCircle(SkIntToScalar(length/2), SkIntToScalar(length/2), SkIntToScalar(length/4),
+                      circlePaint);
+}
+
+// creates a linear gradient shader
+static SkShader* make_linear_gradient_shader(int length) {
+    SkPoint pts[2];
+    SkColor colors[2];
+    pts[0].set(0, 0);
+    pts[1].set(SkIntToScalar(length), 0);
+    colors[0] = SK_ColorBLUE;
+    colors[1] = SkColorSetARGB(0, 0, 0, 0xFF);
+    return SkGradientShader::CreateLinear(pts, colors, nullptr, 2, SkShader::kClamp_TileMode);
+}
+
+
+class ComposeShaderBitmapGM : public skiagm::GM {
+public:
+    ComposeShaderBitmapGM() {
+        draw_color_bm(&fColorBitmap, squareLength);
+        draw_alpha8_bm(&fAlpha8Bitmap, squareLength);
+        SkMatrix s;
+        s.reset();
+        fColorBitmapShader = new SkBitmapProcShader(fColorBitmap, SkShader::kRepeat_TileMode,
+                                                    SkShader::kRepeat_TileMode, &s);
+        fAlpha8BitmapShader = new SkBitmapProcShader(fAlpha8Bitmap, SkShader::kRepeat_TileMode,
+                                                     SkShader::kRepeat_TileMode, &s);
+        fLinearGradientShader = make_linear_gradient_shader(squareLength);
+    }
+    ~ComposeShaderBitmapGM() {
+        SkSafeUnref(fColorBitmapShader);
+        SkSafeUnref(fAlpha8BitmapShader);
+        SkSafeUnref(fLinearGradientShader);
+    }
+
+protected:
+    SkString onShortName() override {
+        return SkString("composeshader_bitmap");
+    }
+
+    SkISize onISize() override {
+        return SkISize::Make(7 * (squareLength + 5), 2 * (squareLength + 5));
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        SkAutoTUnref<SkXfermode> xfer(SkXfermode::Create(SkXfermode::kDstOver_Mode));
+
+        // gradient should appear over color bitmap
+        SkAutoTUnref<SkShader> shader0(new SkComposeShader(fLinearGradientShader,
+                                                           fColorBitmapShader,
+                                                           xfer));
+        // gradient should appear over alpha8 bitmap colorized by the paint color
+        SkAutoTUnref<SkShader> shader1(new SkComposeShader(fLinearGradientShader,
+                                                           fAlpha8BitmapShader,
+                                                           xfer));
+
+        SkShader* shaders[] = { shader0.get(), shader1.get() };
+
+        SkPaint paint;
+        paint.setColor(SK_ColorYELLOW);
+
+        const SkRect r = SkRect::MakeXYWH(0, 0, SkIntToScalar(squareLength),
+                                          SkIntToScalar(squareLength));
+
+        for (size_t y = 0; y < SK_ARRAY_COUNT(shaders); ++y) {
+            SkShader* shader = shaders[y];
+            canvas->save();
+            for (int alpha = 0xFF; alpha > 0; alpha -= 0x28) {
+                paint.setAlpha(alpha);
+                paint.setShader(shader);
+                canvas->drawRect(r, paint);
+
+                canvas->translate(r.width() + 5, 0);
+            }
+            canvas->restore();
+            canvas->translate(0, r.height() + 5);
+        }
+    }
+private:
+    /** This determines the length and width of the bitmaps used in the SkComposeShaders.  Values
+     *  above 20 may cause an SkASSERT to fail in SkSmallAllocator. However, larger values will
+     *  work in a release build.  You can change this parameter and then compile a release build
+     *  to have this GM draw larger bitmaps for easier visual inspection.
+     */
+    static const int squareLength = 20;
+
+    SkBitmap fColorBitmap;
+    SkBitmap fAlpha8Bitmap;
+    SkShader* fColorBitmapShader;
+    SkShader* fAlpha8BitmapShader;
+    SkShader* fLinearGradientShader;
+
+    typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM( return new ComposeShaderGM; )
 DEF_GM( return new ComposeShaderAlphaGM; )
+DEF_GM( return new ComposeShaderBitmapGM; )