add SkPixmap and external locking to bitmaps

include/core/SkImageInfo.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageInfo_DEFINED
 #define SkImageInfo_DEFINED
 
@@ skipping 93 matching lines @@
 }
 
 static inline size_t SkColorTypeMinRowBytes(SkColorType ct, int width) {
     return width * SkColorTypeBytesPerPixel(ct);
 }
 
 static inline bool SkColorTypeIsValid(unsigned value) {
     return value <= kLastEnum_SkColorType;
 }
 
+static inline size_t SkColorTypeComputeOffset(SkColorType ct, int x, int y, size_t rowBytes) {
+    int shift = 0;
+    switch (SkColorTypeBytesPerPixel(ct)) {
+        case 4: shift = 2; break;
+        case 2: shift = 1; break;
+        case 1: shift = 0; break;
+        default: return 0;
+    }
+    return y * rowBytes + (x << shift);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 /**
  *  Return true if alphaType is supported by colorType. If there is a canonical
  *  alphaType for this colorType, return it in canonical.
  */
 bool SkColorTypeValidateAlphaType(SkColorType colorType, SkAlphaType alphaType,
                                   SkAlphaType* canonical = NULL);
 
 ///////////////////////////////////////////////////////////////////////////////
@@ skipping 116 matching lines @@
     }
 
     uint64_t minRowBytes64() const {
         return sk_64_mul(fWidth, this->bytesPerPixel());
     }
 
     size_t minRowBytes() const {
         return (size_t)this->minRowBytes64();
     }
 
+    size_t computeOffset(int x, int y, size_t rowBytes) const {
+        SkASSERT((unsigned)x < (unsigned)fWidth);
+        SkASSERT((unsigned)y < (unsigned)fHeight);
+        return SkColorTypeComputeOffset(fColorType, x, y, rowBytes);
+    }
+
     bool operator==(const SkImageInfo& other) const {
         return 0 == memcmp(this, &other, sizeof(other));
     }
     bool operator!=(const SkImageInfo& other) const {
         return 0 != memcmp(this, &other, sizeof(other));
     }
 
     void unflatten(SkReadBuffer&);
     void flatten(SkWriteBuffer&) const;
 
@@ skipping 31 matching lines @@
         , fHeight(height)
         , fColorType(ct)
         , fAlphaType(at)
         , fProfileType(pt)
     {}
 
     SkColorProfileType  fProfileType;
 };
 
 #endif