Implement an SkPaint-based image filter

src/effects/SkPaintImageFilter.cpp

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkPaintImageFilter.h"
+#include "SkBitmap.h"
+#include "SkCanvas.h"
+#include "SkDevice.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+SkImageFilter* SkPaintImageFilter::Create(const SkPaint& paint, const CropRect* cropRect) {
+    return new SkPaintImageFilter(paint, cropRect);
+}
+
+SkPaintImageFilter::SkPaintImageFilter(const SkPaint& paint, const CropRect* cropRect)
+  : INHERITED(0, nullptr, cropRect)
+  , fPaint(paint) {
+}
+
+SkFlattenable* SkPaintImageFilter::CreateProc(SkReadBuffer& buffer) {
+    SK_IMAGEFILTER_UNFLATTEN_COMMON(common, 0);
+    SkPaint paint;
+    buffer.readPaint(&paint);
+    return Create(paint, &common.cropRect());
+}
+
+void SkPaintImageFilter::flatten(SkWriteBuffer& buffer) const {
+    this->INHERITED::flatten(buffer);
+    buffer.writePaint(fPaint);
+}
+
+bool SkPaintImageFilter::onFilterImage(Proxy* proxy,
+                                            const SkBitmap& source,
+                                            const Context& ctx,
+                                            SkBitmap* result,
+                                            SkIPoint* offset) const {
+    SkIRect bounds;
+    if (!this->applyCropRect(ctx, source, SkIPoint::Make(0, 0), &bounds)) {
+        return false;
+    }
+
+    SkAutoTUnref<SkBaseDevice> device(proxy->createDevice(bounds.width(),
+                                                          bounds.height()));
+    if (nullptr == device.get()) {
+        return false;
+    }
+    SkCanvas canvas(device.get());
+
+    SkMatrix matrix(ctx.ctm());
+    matrix.postTranslate(SkIntToScalar(-bounds.left()), SkIntToScalar(-bounds.top()));
+    SkRect rect = SkRect::MakeWH(SkIntToScalar(bounds.width()), SkIntToScalar(bounds.height()));
+    SkMatrix inverse;
+    if (matrix.invert(&inverse)) {
+        inverse.mapRect(&rect);
+    }
+    canvas.setMatrix(matrix);
+    canvas.drawRect(rect, fPaint);
+
+    *result = device.get()->accessBitmap(false);
+    offset->fX = bounds.fLeft;
+    offset->fY = bounds.fTop;
+    return true;
+}
+
+bool SkPaintImageFilter::canComputeFastBounds() const {
+    // http:skbug.com/4627: "make computeFastBounds and onFilterBounds() CropRect-aware"
+    // computeFastBounds() doesn't currently take the crop rect into account,
+    // so we can't compute it. If a full crop rect is set, we should return true here.
+    return false;
+}
+
+#ifndef SK_IGNORE_TO_STRING
+void SkPaintImageFilter::toString(SkString* str) const {
+    str->appendf("SkPaintImageFilter: (");
+    str->append(")");
+}
+#endif