optimize the disable-caching case for SkImage::readPixels

src/image/SkImage.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkBitmapCache.h"
 #include "SkCanvas.h"
@@ skipping 39 matching lines @@
 bool SkImage::readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
                            int srcX, int srcY, CachingHint chint) const {
     SkReadPixelsRec rec(dstInfo, dstPixels, dstRowBytes, srcX, srcY);
     if (!rec.trim(this->width(), this->height())) {
         return false;
     }
     return as_IB(this)->onReadPixels(rec.fInfo, rec.fPixels, rec.fRowBytes, rec.fX, rec.fY, chint);
 }
 
 bool SkImage::scalePixels(const SkPixmap& dst, SkFilterQuality quality, CachingHint chint) const {
+    if (this->width() == dst.width() && this->height() == dst.height()) {
+        return this->readPixels(dst, 0, 0, chint);
+    }
+
     // Idea: If/when SkImageGenerator supports a native-scaling API (where the generator itself
     //       can scale more efficiently) we should take advantage of it here.
     //
     SkBitmap bm;
     if (as_IB(this)->getROPixels(&bm, chint)) {
         bm.lockPixels();
         SkPixmap pmap;
         // Note: By calling the pixmap scaler, we never cache the final result, so the chint
         //       is (currently) only being applied to the getROPixels. If we get a request to
         //       also attempt to cache the final (scaled) result, we would add that logic here.
@@ skipping 343 matching lines @@
 
 SkImage* SkImage::NewFromAdoptedTexture(GrContext*, const GrBackendTextureDesc&, SkAlphaType) {
     return nullptr;
 }
 
 SkImage* SkImage::NewFromTextureCopy(GrContext*, const GrBackendTextureDesc&, SkAlphaType) {
     return nullptr;
 }
 
 #endif