Image filters: implement SkImage::makeWithFilter().

src/image/SkImage.cpp

Index: src/image/SkImage.cpp
diff --git a/src/image/SkImage.cpp b/src/image/SkImage.cpp
index 1970c57839912db2d4288f8b32d9af5f780f72bb..8bf1f247b07a209d2598b1c7a65b2d52de022525 100644
--- a/src/image/SkImage.cpp
+++ b/src/image/SkImage.cpp
@@ -10,6 +10,7 @@
 #include "SkCanvas.h"
 #include "SkData.h"
 #include "SkImageEncoder.h"
+#include "SkImageFilter.h"
 #include "SkImageGenerator.h"
 #include "SkImagePriv.h"
 #include "SkImageShader.h"
@@ -19,6 +20,7 @@
 #include "SkPixelRef.h"
 #include "SkPixelSerializer.h"
 #include "SkReadPixelsRec.h"
+#include "SkSpecialImage.h"
 #include "SkString.h"
 #include "SkSurface.h"
 
@@ -342,6 +344,45 @@ sk_sp<SkImage> SkImage::MakeFromPicture(sk_sp<SkPicture> picture, const SkISize&
                                                               matrix, paint));
 }
 
+sk_sp<SkImage> SkImage::makeWithFilter(const SkImageFilter* filter, const SkIRect& subset,
+                                       const SkIRect& clipBounds, SkIRect* outSubset,
+                                       SkIPoint* offset) const {
+  if (!filter || !outSubset || !offset || !this->bounds().contains(subset)) {
+      return nullptr;
+  }
+  sk_sp<SkSpecialImage> srcSpecialImage = SkSpecialImage::MakeFromImage(
+      subset, sk_ref_sp(const_cast<SkImage*>(this)));
+  if (!srcSpecialImage) {
+      return nullptr;
+  }
+
+  // FIXME: build a cache here.
+  SkImageFilter::Context context(SkMatrix::I(), clipBounds, nullptr);
+  sk_sp<SkSpecialImage> result =
+      filter->filterImage(srcSpecialImage.get(), context, offset);
+
+  if (!result) {
+      return nullptr;
+  }
+
+  SkIRect fullSize = SkIRect::MakeWH(result->width(), result->height());
+#if SK_SUPPORT_GPU
+  if (result->isTextureBacked()) {
+    GrContext* context = result->getContext();
+    sk_sp<GrTexture> texture = result->asTextureRef(context);
+    fullSize = SkIRect::MakeWH(texture->width(), texture->height());
+  }
+#endif
+  *outSubset = SkIRect::MakeWH(result->width(), result->height());
+  if (!outSubset->intersect(clipBounds.makeOffset(-offset->x(), -offset->y()))) {
+      return nullptr;
+  }
+  offset->fX += outSubset->x();
+  offset->fY += outSubset->y();
+  // This isn't really a "tight" subset, but includes any texture padding.
+  return result->makeTightSubset(fullSize);
+}
+
 bool SkImage::isLazyGenerated() const {
     return as_IB(this)->onIsLazyGenerated();
 }