Add rowBytesAsPixels and shiftPerPixel to SkPixmap

include/core/SkPixmap.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPixmap_DEFINED
 #define SkPixmap_DEFINED
 
@@ skipping 53 matching lines @@
     SkColorTable* ctable() const { return fCTable; }
 
     int width() const { return fInfo.width(); }
     int height() const { return fInfo.height(); }
     SkColorType colorType() const { return fInfo.colorType(); }
     SkAlphaType alphaType() const { return fInfo.alphaType(); }
     bool isOpaque() const { return fInfo.isOpaque(); }
 
     SkIRect bounds() const { return SkIRect::MakeWH(this->width(), this->height()); }
 
+    /**
+     *  Return the rowbytes expressed as a number of pixels (like width and height).
+     */
+    int rowBytesAsPixels() const { return int(fRowBytes >> this->shiftPerPixel()); }
+
+    /**
+     *  Return the shift amount per pixel (i.e. 0 for 1-byte per pixel, 1 for 2-bytes per pixel
+     *  colortypes, 2 for 4-bytes per pixel colortypes). Return 0 for kUnknown_SkColorType.
+     */
+    int shiftPerPixel() const { return fInfo.bytesPerPixel() >> 1; }
+
     uint64_t getSize64() const { return sk_64_mul(fInfo.height(), fRowBytes); }
     uint64_t getSafeSize64() const { return fInfo.getSafeSize64(fRowBytes); }
     size_t getSafeSize() const { return fInfo.getSafeSize(fRowBytes); }
 
     const void* addr(int x, int y) const {
         return (const char*)fPixels + fInfo.computeOffset(x, y, fRowBytes);
     }
     const uint8_t* addr8() const {
         SkASSERT(1 == SkColorTypeBytesPerPixel(fInfo.colorType()));
         return reinterpret_cast<const uint8_t*>(fPixels);
@@ skipping 145 matching lines @@
 private:
     void        (*fUnlockProc)(void*);
     void*       fUnlockContext;
     SkPixmap    fPixmap;
     bool        fIsLocked;
 
     friend class SkBitmap;
 };
 
 #endif