Add SkBitmap::readPixels() and reimplement copyTo and SkCanvas::readPixels

include/core/SkBitmap.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBitmap_DEFINED
 #define SkBitmap_DEFINED
 
@@ skipping 573 matching lines @@
      *                   will be used.
      *  @return true if the copy was made.
      */
     bool copyTo(SkBitmap* dst, SkColorType ct, Allocator* = NULL) const;
 
     bool copyTo(SkBitmap* dst, Allocator* allocator = NULL) const {
         return this->copyTo(dst, this->colorType(), allocator);
     }
 
     /**
+     *  Copy the bitmap's pixels into the specified buffer (pixels + rowBytes),
+     *  converting them into the requested format (SkImageInfo). The src pixels are read
+     *  starting at the specified (srcX,srcY) offset, relative to the top-left corner.
+     *
+     *  The specified ImageInfo and (srcX,srcY) offset specifies a source rectangle
+     *
+     *      srcR.setXYWH(srcX, srcY, dstInfo.width(), dstInfo.height());
+     *
+     *  srcR is intersected with the bounds of the bitmap. If this intersection is not empty,
+     *  then we have two sets of pixels (of equal size). Replace the dst pixels with the
+     *  corresponding src pixels, performing any colortype/alphatype transformations needed
+     *  (in the case where the src and dst have different colortypes or alphatypes).
+     *
+     *  This call can fail, returning false, for several reasons:
+     *  - If srcR does not intersect the bitmap bounds.
+     *  - If the requested colortype/alphatype cannot be converted from the src's types.
+     *  - If the src pixels are not available.
+     */
+    bool readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
+                    int srcX, int srcY) const;
+
+    /**
      *  Returns true if this bitmap's pixels can be converted into the requested
      *  colorType, such that copyTo() could succeed.
      */
     bool canCopyTo(SkColorType colorType) const;
 
     /** Makes a deep copy of this bitmap, keeping the copied pixels
      *  in the same domain as the source: If the src pixels are allocated for
      *  the cpu, then so will the dst. If the src pixels are allocated on the
      *  gpu (typically as a texture), the it will do the same for the dst.
      *  If the request cannot be fulfilled, returns false and dst is unmodified.
@@ skipping 244 matching lines @@
 #ifdef SK_SUPPORT_LEGACY_BITMAP_CONFIG
 ///////////////////////////////////////////////////////////////////////////////
 //
 // Helpers until we can fully deprecate SkBitmap::Config
 //
 SK_API SkBitmap::Config SkColorTypeToBitmapConfig(SkColorType);
 SK_API SkColorType SkBitmapConfigToColorType(SkBitmap::Config);
 #endif
 
 #endif