ui/gfx: optimize color format conversions by using memcpy in jpeg_codec.cc

ui/gfx/codec/jpeg_codec.cc

 // Copyright (c) 2011 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 "ui/gfx/codec/jpeg_codec.h"
 
 #include <setjmp.h>
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 132 matching lines @@
   state->out->resize(state->image_buffer_used);
 }
 
 #if !defined(JCS_EXTENSIONS)
 // Converts RGBA to RGB (removing the alpha values) to prepare to send data to
 // libjpeg. This converts one row of data in rgba with the given width in
 // pixels the the given rgb destination buffer (which should have enough space
 // reserved for the final data).
 void StripAlpha(const unsigned char* rgba, int pixel_width, unsigned char* rgb)
 {
-  for (int x = 0; x < pixel_width; x++) {
-    const unsigned char* pixel_in = &rgba[x * 4];
-    unsigned char* pixel_out = &rgb[x * 3];
-    pixel_out[0] = pixel_in[0];
-    pixel_out[1] = pixel_in[1];
-    pixel_out[2] = pixel_in[2];
-  }
+  for (int x = 0; x < pixel_width; x++)
+    memcpy(&rgb[x * 3], &rgba[x * 4], 3);
 }
 
 // Converts BGRA to RGB by reordering the color components and dropping the
 // alpha. This converts  one row of data in rgba with the given width in
 // pixels the the given rgb destination buffer (which should have enough space
 // reserved for the final data).
 void BGRAtoRGB(const unsigned char* bgra, int pixel_width, unsigned char* rgb)
 {
   for (int x = 0; x < pixel_width; x++) {
     const unsigned char* pixel_in = &bgra[x * 4];
@@ skipping 230 matching lines @@
 //   been read to clean up JPEG source manager. NOT called by jpeg_abort() or
 //   jpeg_destroy()."
 void TermSource(j_decompress_ptr cinfo) {
 }
 
 #if !defined(JCS_EXTENSIONS)
 // Converts one row of rgb data to rgba data by adding a fully-opaque alpha
 // value.
 void AddAlpha(const unsigned char* rgb, int pixel_width, unsigned char* rgba) {
   for (int x = 0; x < pixel_width; x++) {
-    const unsigned char* pixel_in = &rgb[x * 3];
-    unsigned char* pixel_out = &rgba[x * 4];
-    pixel_out[0] = pixel_in[0];
-    pixel_out[1] = pixel_in[1];
-    pixel_out[2] = pixel_in[2];
-    pixel_out[3] = 0xff;
+    memcpy(&rgba[x * 4], &rgb[x * 3], 3);
+    rgba[x * 4 + 3] = 0xff;
   }
 }
 
 // Converts one row of RGB data to BGRA by reordering the color components and
 // adding alpha values of 0xff.
 void RGBtoBGRA(const unsigned char* bgra, int pixel_width, unsigned char* rgb)
 {
   for (int x = 0; x < pixel_width; x++) {
     const unsigned char* pixel_in = &bgra[x * 3];
     unsigned char* pixel_out = &rgb[x * 4];
@@ skipping 196 matching lines @@
   int data_length = w * h * 4;
 
   SkBitmap* bitmap = new SkBitmap();
   bitmap->allocN32Pixels(w, h);
   memcpy(bitmap->getAddr32(0, 0), &data_vector[0], data_length);
 
   return bitmap;
 }
 
 }  // namespace gfx