add applyFilter() to SkImage

src/image/SkImage.cpp

Index: src/image/SkImage.cpp
diff --git a/src/image/SkImage.cpp b/src/image/SkImage.cpp
index af9c27592c527e1383136f999ba56ede955eb07d..3ad80043da2f49e841e546346efca82a0f712171 100644
--- a/src/image/SkImage.cpp
+++ b/src/image/SkImage.cpp
@@ -67,6 +67,81 @@ void SkImage::preroll(GrContext* ctx) const {
     }
 }
 
+SkImage* SkImage::applyFilter(SkImageFilter* filter, SkIPoint* offset,
+                              bool forceResultToOriginalSize) const {
+    if (!filter) {
+        return nullptr;
+    }
+
+    SkIPoint offsetStorage;
+    if (!offset) {
+        offset = &offsetStorage;
+    }
+    return as_IB(this)->onApplyFilter(filter, offset, forceResultToOriginalSize);
+}
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+#include "SkImageFilter.h"
+#include "SkBitmapDevice.h"
+
+static SkIRect compute_fast_ibounds(SkImageFilter* filter, const SkIRect& srcBounds) {
+    SkRect fastBounds;
+    fastBounds.set(srcBounds);
+    filter->computeFastBounds(fastBounds, &fastBounds);
+    return fastBounds.roundOut();
+}
+
+class SkRasterImageFilterProxy : public SkImageFilter::Proxy {
+public:
+    SkBaseDevice* createDevice(int width, int height) override {
+        return SkBitmapDevice::Create(SkImageInfo::MakeN32Premul(width, height));
+    }
+
+    bool filterImage(const SkImageFilter*, const SkBitmap&, const SkImageFilter::Context&,
+                     SkBitmap*, SkIPoint*) override {
+        return false;
+    }
+};
+
+SkImage* SkImage_Base::onApplyFilter(SkImageFilter* filter, SkIPoint* offsetResult,
+                                     bool forceResultToOriginalSize) const {
+    SkBitmap src;
+    if (!this->getROPixels(&src)) {
+        return nullptr;
+    }
+
+    const SkIRect srcBounds = SkIRect::MakeWH(this->width(), this->height());
+
+    if (forceResultToOriginalSize) {
+        const SkIRect clipBounds = srcBounds;
+        SkRasterImageFilterProxy proxy;
+        SkImageFilter::Context ctx(SkMatrix::I(), clipBounds, SkImageFilter::Cache::Get());
+
+        SkBitmap dst;
+        if (filter->filterImage(&proxy, src, ctx, &dst, offsetResult)) {
+            dst.setImmutable();
+            return SkImage::NewFromBitmap(dst);
+        }
+    } else {
+        const SkIRect dstR = compute_fast_ibounds(filter, srcBounds);
+
+        SkImageInfo info = SkImageInfo::MakeN32Premul(dstR.width(), dstR.height());
+        SkAutoTUnref<SkSurface> surface(this->onNewSurface(info));
+
+        SkPaint paint;
+        paint.setImageFilter(filter);
+        surface->getCanvas()->drawImage(this, SkIntToScalar(-dstR.x()), SkIntToScalar(-dstR.y()),
+                                        &paint);
+
+        offsetResult->set(dstR.x(), dstR.y());
+        return surface->newImageSnapshot();
+    }
+    return nullptr;
+}
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
 SkShader* SkImage::newShader(SkShader::TileMode tileX,
                              SkShader::TileMode tileY,
                              const SkMatrix* localMatrix) const {