Implement a resize image filter. This is needed for the "filterRes" feature in SVG filter effects, …

src/effects/SkResizeImageFilter.cpp

+/*
+ * Copyright 2013 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 "SkResizeImageFilter.h"
+#include "SkBitmap.h"
+#include "SkCanvas.h"
+#include "SkDevice.h"
+#include "SkColorPriv.h"
+#include "SkFlattenableBuffers.h"
+#include "SkMatrix.h"
+#include "SkRect.h"
+
+SkResizeImageFilter::SkResizeImageFilter(const SkSize& scale, SkPaint::FilterLevel filterLevel, SkImageFilter* input)
+  : INHERITED(input),
+    fScale(scale),
+    fFilterLevel(filterLevel) {
+}
+
+SkResizeImageFilter::SkResizeImageFilter(SkFlattenableReadBuffer& buffer)
+  : INHERITED(1, buffer) {
+    fScale.fWidth = buffer.readScalar();
+    fScale.fHeight = buffer.readScalar();
+    fFilterLevel = static_cast<SkPaint::FilterLevel>(buffer.readInt());
+}
+
+void SkResizeImageFilter::flatten(SkFlattenableWriteBuffer& buffer) const {
+    this->INHERITED::flatten(buffer);
+    buffer.writeScalar(fScale.fWidth);
+    buffer.writeScalar(fScale.fHeight);
+    buffer.writeInt(fFilterLevel);
+}
+
+SkResizeImageFilter::~SkResizeImageFilter() {
+}
+
+bool SkResizeImageFilter::onFilterImage(Proxy* proxy,
+                                         const SkBitmap& source,
+                                         const SkMatrix& matrix,
+                                         SkBitmap* result,
+                                         SkIPoint* offset) {
+    SkBitmap src = source;
+    SkIPoint srcOffset = SkIPoint::Make(0, 0);
+    if (getInput(0) && !getInput(0)->filterImage(proxy, source, matrix, &src, &srcOffset)) {
+        return false;
+    }
+
+    SkRect dstRect;
+    SkIRect srcBounds, dstBounds;
+    src.getBounds(&srcBounds);
+    srcBounds.offset(srcOffset);
+    SkRect srcRect = SkRect::Make(srcBounds);
+    SkMatrix dstMatrix = matrix;
+    dstMatrix.preScale(fScale.fWidth, fScale.fHeight);
+    dstMatrix.mapRect(&dstRect, srcRect);
+    dstRect.roundOut(&dstBounds);
+
+    SkAutoTUnref<SkBaseDevice> device(proxy->createDevice(dstBounds.width(), dstBounds.height()));
+    if (NULL == device.get()) {
+        return false;
+    }
+
+    SkCanvas canvas(device.get());
+    canvas.translate(-SkIntToScalar(dstBounds.fLeft), -SkIntToScalar(dstBounds.fTop));
+    SkPaint paint;
+
+    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
+    paint.setFilterLevel(fFilterLevel);
+    canvas.drawBitmapRectToRect(src, &srcRect, dstRect, &paint);

[reed1, 2014/01/13 22:02:57]

can you instead call canvas.concat(dstMatrix) followed by drawBitmap?

[Stephen White, 2014/01/14 21:45:43]

Done.

+
+    *result = device.get()->accessBitmap(false);
+    offset->fX = dstBounds.fLeft;
+    offset->fY = dstBounds.fTop;
+    return true;
+}