Copy the (early prototype of) remoting in Chrome into the public tree....

remoting/host/differ_block.cc

+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "differ_block.h"
+
+#include <stdlib.h>
+
+namespace remoting {
+
+// TODO(fbarchard): Use common header for block size.
+int kBlockWidth = 32;
+int kBlockHeight = 32;
+int kBytesPerPixel = 3;
+
+int BlockDifference(const uint8* image1, const uint8* image2, int stride) {
+  int diff = 0;
+  for (int y = 0; y < kBlockHeight; ++y) {
+    for (int x = 0; x < kBlockWidth * kBytesPerPixel; ++x) {
+      diff += abs(image1[x] - image2[x]);
+    }
+    image1 += stride;
+    image2 += stride;
+  }
+  return diff;
+}
+
+}  // namespace remoting