Proposal for SkImageGenerator::canDecodeAndScale API

src/core/SkImageGenerator.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImageGenerator.h"
 #include "SkNextID.h"
 
@@ skipping 180 matching lines @@
         // allocate space for all the pixels.
         ctable->dangerous_overwriteColors(ctStorage, ctCount);
     } else {
         SkASSERT(kIndex_8_SkColorType != bitmap->colorType());
         // we should be the only owner
         SkASSERT(ctable->unique());
     }
     return true;
 }
 
+SkImageGenerator::Result SkImageGenerator::canDecodeAndScale(const SkColorType colorType, const SkScalar scale, SkISize* availableSize, SkISize* lowerSize) {
+    return this->onCanDecodeAndScale(colorType, scale, availableSize, lowerSize);
+}
+
+SkImageGenerator::Result SkImageGenerator::onCanDecodeAndScale(const SkColorType colorType, const SkScalar scale, SkISize* availableSize, SkISize* lowerSize) {
+    unsigned result = SkImageGenerator::kNotAvailable;
+    if (colorType == fInfo.colorType())
+        result |= SkImageGenerator::kDecode;
+    if (scale == SK_Scalar1) {
+        result |= SkImageGenerator::kScale;
+        if (availableSize) {
+            availableSize->fWidth = fInfo.width();
+            availableSize->fHeight = fInfo.height();
+        }
+        if (lowerSize) {
+            availableSize->fWidth = availableSize->fHeight = 0;
+        }
+    }
+    return static_cast<SkImageGenerator::Result>(result);
+}
+
+
 #include "SkGraphics.h"
 
 static SkGraphics::ImageGeneratorFromEncodedFactory gFactory;
 
 SkGraphics::ImageGeneratorFromEncodedFactory
 SkGraphics::SetImageGeneratorFromEncodedFactory(ImageGeneratorFromEncodedFactory factory)
 {
     ImageGeneratorFromEncodedFactory prev = gFactory;
     gFactory = factory;
     return prev;
 }
 
 SkImageGenerator* SkImageGenerator::NewFromEncoded(SkData* data) {
     if (nullptr == data) {
         return nullptr;
     }
     if (gFactory) {
         if (SkImageGenerator* generator = gFactory(data)) {
             return generator;
         }
     }
     return SkImageGenerator::NewFromEncodedImpl(data);
 }