optimize the disable-caching case for SkImage::readPixels

src/image/SkImage_Generator.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImage_Base.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
@@ skipping 23 matching lines @@
     SkAutoTDelete<SkImageCacherator> fCache;
 
     typedef SkImage_Base INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 bool SkImage_Generator::onReadPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRB,
                                      int srcX, int srcY, CachingHint chint) const {
     SkBitmap bm;
+    if (kDisallow_CachingHint == chint) {
+        if (fCache->lockAsBitmapOnlyIfAlreadyCached(&bm)) {
+            return bm.readPixels(dstInfo, dstPixels, dstRB, srcX, srcY);
+        } else {
+            // Try passing the caller's buffer directly down to the generator. If this fails we
+            // may still succeed in the general case, as the generator may prefer some other
+            // config, which we could then convert via SkBitmap::readPixels.
+            if (fCache->directGeneratePixels(dstInfo, dstPixels, dstRB, srcX, srcY)) {
+                return true;
+            }
+            // else fall through
+        }
+    }
+
     if (this->getROPixels(&bm, chint)) {
         return bm.readPixels(dstInfo, dstPixels, dstRB, srcX, srcY);
     }
     return false;
 }
 
 const void* SkImage_Generator::onPeekPixels(SkImageInfo* infoPtr, size_t* rowBytesPtr) const {
     return NULL;
 }
 
@@ skipping 25 matching lines @@
     return surface->newImageSnapshot();
 }
 
 SkImage* SkImage::NewFromGenerator(SkImageGenerator* generator, const SkIRect* subset) {
     SkImageCacherator* cache = SkImageCacherator::NewFromGenerator(generator, subset);
     if (!cache) {
         return nullptr;
     }
     return new SkImage_Generator(cache);
 }