Implement srcRect and dstRect functionality in SkBitmapSource. This is required for the "preserveAs…

src/effects/SkBitmapSource.cpp

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapSource.h"
+#include "SkDevice.h"
+#include "SkCanvas.h"
+#include "SkFlattenableBuffers.h"
+#include "SkValidationUtils.h"
 
-SkBitmapSource::SkBitmapSource(const SkBitmap& bitmap)
+SkBitmapSource::SkBitmapSource(const SkBitmap& bitmap, const SkRect* srcRect, const SkRect* dstRect)
   : INHERITED(0, 0),
-    fBitmap(bitmap) {
+    fBitmap(bitmap),
+    fSrcRect(srcRect ? *srcRect : SkRect::MakeWH(bitmap.width(), bitmap.height())),
+    fDstRect(dstRect ? *dstRect : fSrcRect) {
 }
 
 SkBitmapSource::SkBitmapSource(SkFlattenableReadBuffer& buffer)
   : INHERITED(0, buffer) {
     fBitmap.unflatten(buffer);
+    buffer.readRect(&fSrcRect);
+    buffer.readRect(&fDstRect);
+    buffer.validate(SkIsValidRect(fSrcRect) && SkIsValidRect(fDstRect));
 }
 
 void SkBitmapSource::flatten(SkFlattenableWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     fBitmap.flatten(buffer);
+    buffer.writeRect(fSrcRect);
+    buffer.writeRect(fDstRect);
 }
 
-bool SkBitmapSource::onFilterImage(Proxy*, const SkBitmap&, const SkMatrix&,
+bool SkBitmapSource::onFilterImage(Proxy* proxy, const SkBitmap&, const SkMatrix& matrix,
                                    SkBitmap* result, SkIPoint* offset) {
-    *result = fBitmap;
+    SkRect bounds, dstRect;
+    fBitmap.getBounds(&bounds);
+    matrix.mapRect(&dstRect, fDstRect);
+    if (fSrcRect == bounds && dstRect == bounds) {
+        *result = fBitmap;
+        return true;
+    }
+    SkAutoTUnref<SkBaseDevice> device(proxy->createDevice(SkScalarCeilToInt(dstRect.width()), SkScalarCeilToInt(dstRect.height())));
+    if (NULL == device.get()) {
+        return false;
+    }
+
+    SkCanvas canvas(device.get());
+    SkPaint paint;
+
+    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
+    // FIXME: this probably shouldn't be necessary, but drawBitmapRectToRect asserts None filtering when it's translate-only
+    paint.setFilterLevel(fSrcRect.width() == dstRect.width() && fSrcRect.height() == dstRect.height() ? SkPaint::kNone_FilterLevel : SkPaint::kMedium_FilterLevel);
+    canvas.drawBitmapRectToRect(fBitmap, &fSrcRect, SkRect::MakeWH(dstRect.width(), dstRect.height()), &paint);
+
+    *result = device.get()->accessBitmap(false);
+    offset->fX += dstRect.fLeft;
+    offset->fY += dstRect.fTop;
     return true;
 }