add SkImage::NewFromPicture and a GM to test it

BUG=skia:
TBR=

Review URL: https://codereview.chromium.org/1288403002

gm/image_pict.cpp

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2015 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 "SkImage.h"
+#include "SkPictureRecorder.h"
+
+#if SK_SUPPORT_GPU
+#include "GrContext.h"
+#endif
+
+static void draw_something(SkCanvas* canvas, const SkRect& bounds) {
+    SkPaint paint;
+    paint.setAntiAlias(true);
+    paint.setColor(SK_ColorRED);
+    paint.setStyle(SkPaint::kStroke_Style);
+    paint.setStrokeWidth(10);
+    canvas->drawRect(bounds, paint);
+    paint.setStyle(SkPaint::kFill_Style);
+    paint.setColor(SK_ColorBLUE);
+    canvas->drawOval(bounds, paint);
+}
+
+/*
+ *  Exercise drawing pictures inside an image, showing that the image version is pixelated
+ *  (correctly) when it is inside an image.
+ */
+class ImagePictGM : public skiagm::GM {
+    SkAutoTUnref<SkPicture> fPicture;
+    SkAutoTUnref<SkImage>   fImage0;
+    SkAutoTUnref<SkImage>   fImage1;
+public:
+    ImagePictGM() {}
+
+protected:
+    SkString onShortName() override {
+        return SkString("image-picture");
+    }
+
+    SkISize onISize() override {
+        return SkISize::Make(850, 450);
+    }
+
+    void onOnceBeforeDraw() override {
+        const SkRect bounds = SkRect::MakeXYWH(100, 100, 100, 100);
+        SkPictureRecorder recorder;
+        draw_something(recorder.beginRecording(bounds), bounds);
+        fPicture.reset(recorder.endRecording());
+
+        // extract enough just for the oval.
+        const SkISize size = SkISize::Make(100, 100);
+
+        SkMatrix matrix;
+        matrix.setTranslate(-100, -100);
+        fImage0.reset(SkImage::NewFromPicture(fPicture, size, &matrix, nullptr));
+        matrix.postTranslate(-50, -50);
+        matrix.postRotate(45);
+        matrix.postTranslate(50, 50);
+        fImage1.reset(SkImage::NewFromPicture(fPicture, size, &matrix, nullptr));
+    }
+
+    void drawSet(SkCanvas* canvas) const {
+        SkMatrix matrix = SkMatrix::MakeTrans(-100, -100);
+        canvas->drawPicture(fPicture, &matrix, nullptr);
+        canvas->drawImage(fImage0, 150, 0);
+        canvas->drawImage(fImage1, 300, 0);
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        canvas->translate(20, 20);
+
+        this->drawSet(canvas);
+
+        canvas->save();
+        canvas->translate(0, 130);
+        canvas->scale(0.25f, 0.25f);
+        this->drawSet(canvas);
+        canvas->restore();
+
+        canvas->save();
+        canvas->translate(0, 200);
+        canvas->scale(2, 2);
+        this->drawSet(canvas);
+        canvas->restore();
+    }
+
+private:
+    typedef skiagm::GM INHERITED;
+};
+DEF_GM( return new ImagePictGM; )
+

include/core/SkImage.h

@@ -20,6 +20,7 @@ class SkCanvas;
 class SkColorTable;
 class SkImageGenerator;
 class SkPaint;
+class SkPicture;
 class SkString;
 class SkSurface;
 class SkSurfaceProps;
@@ -141,6 +142,11 @@ public:
                                            const SkISize yuvSizes[3],
                                            GrSurfaceOrigin);
 
+    static SkImage* NewFromPicture(const SkPicture*, const SkISize& dimensions,
+                                   const SkMatrix*, const SkPaint*);
+
+    ///////////////////////////////////////////////////////////////////////////////////////////////
+
     int width() const { return fWidth; }
     int height() const { return fHeight; }
     uint32_t uniqueID() const { return fUniqueID; }

src/image/SkImage.cpp

@@ -279,6 +279,14 @@ bool SkImage_Base::onAsLegacyBitmap(SkBitmap* bitmap, LegacyBitmapMode mode) con
     return true;
 }
 
+SkImage* SkImage::NewFromPicture(const SkPicture* picture, const SkISize& dimensions,
+                                 const SkMatrix* matrix, const SkPaint* paint) {
+    if (!picture) {
+        return nullptr;
+    }
+    return NewFromGenerator(SkImageGenerator::NewFromPicture(dimensions, picture, matrix, paint));
+}
+
 //////////////////////////////////////////////////////////////////////////////////////
 
 #if !SK_SUPPORT_GPU