add peekPixels to SkCanvas and SkSurface

gm/peekpixels.cpp

+/*
+ * Copyright 2011 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 "SkCanvas.h"
+#include "SkPath.h"
+#include "SkSurface.h"
+#include "SkPicture.h"
+
+static void draw_content(SkCanvas* canvas) {
+    SkImageInfo info = canvas->imageInfo();
+    SkPaint paint;
+    paint.setAntiAlias(true);
+    canvas->drawCircle(SkScalarHalf(info.width()), SkScalarHalf(info.height()),
+                       SkScalarHalf(info.width()), paint);
+}
+
+class PeekPixelsGM : public skiagm::GM {
+public:
+    PeekPixelsGM() {}
+
+protected:
+    virtual SkString onShortName() SK_OVERRIDE {
+        return SkString("peekpixels");
+    }
+
+    virtual SkISize onISize() SK_OVERRIDE {
+        return SkISize::Make(640, 480);
+    }
+
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+        SkImageInfo info = SkImageInfo::MakeN32Premul(100, 100);
+        SkAutoTUnref<SkSurface> surface(canvas->newSurface(info));
+        if (surface.get()) {
+            SkCanvas* surfCanvas = surface->getCanvas();
+            
+            draw_content(surfCanvas);
+            SkBitmap bitmap;
+            
+            // test peekPixels
+            {
+                SkImageInfo info;
+                size_t rowBytes;
+                const void* addr = surfCanvas->peekPixels(&info, &rowBytes);
+                if (addr && bitmap.installPixels(info, const_cast<void*>(addr),
+                                                 rowBytes, NULL, NULL)) {
+                    canvas->drawBitmap(bitmap, 0, 0, NULL);
+                }
+            }
+            
+            // test ROCanvasPixels
+            canvas->translate(120, 0);
+            SkAutoROCanvasPixels ropixels(surfCanvas);
+            if (ropixels.asROBitmap(&bitmap)) {
+                canvas->drawBitmap(bitmap, 0, 0, NULL);
+            }
+            
+            // test Surface
+            canvas->translate(120, 0);
+            surface->draw(canvas, 0, 0, NULL);
+        }
+    }
+
+    virtual uint32_t onGetFlags() const {
+        // we explicitly test peekPixels and readPixels, neither of which
+        // return something for a picture-backed canvas, so we skip that test.
+        return kSkipPicture_Flag;
+    }
+
+private:
+    typedef skiagm::GM INHERITED;
+};
+
+DEF_GM( return SkNEW(PeekPixelsGM); )