Change point down sampling to x = dx / 2 which matches ffmpeg and is lossless on…

Change point down sampling to x = dx / 2 which matches ffmpeg and is lossless on up and then down sample.
BUG=232
TEST=convert.exe -f 0 faces_640x480_P420.yuv face2_352x288_P420.yuv
R=johannkoenig@google.com, ryanpetrie@google.com

Review URL: https://webrtc-codereview.appspot.com/1581005

git-svn-id: http://libyuv.googlecode.com/svn/trunk@707 16f28f9a-4ce2-e073-06de-1de4eb20be90

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 706
+Version: 707
 License: BSD
 License File: LICENSE
 

include/libyuv/version.h

@@ -11,6 +11,6 @@
 #ifndef INCLUDE_LIBYUV_VERSION_H_  // NOLINT
 #define INCLUDE_LIBYUV_VERSION_H_
 
-#define LIBYUV_VERSION 706
+#define LIBYUV_VERSION 707
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_  NOLINT

source/scale.cc

@@ -3232,8 +3232,8 @@ static void ScalePlaneSimple(int src_width, int src_height,
                              const uint8* src_ptr, uint8* dst_ptr) {
   int dx = (Abs(src_width) << 16) / dst_width;
   int dy = (src_height << 16) / dst_height;
-  int x = (dx >= 65536) ? ((dx >> 1) - 32768) : (dx >> 1);
-  int y = (dy >= 65536) ? ((dy >> 1) - 32768) : (dy >> 1);
+  int x = dx >> 1;
+  int y = dy >> 1;
   // Negative src_width means horizontally mirror.
   if (src_width < 0) {
     x += (dst_width - 1) * dx;

source/scale_argb.cc

@@ -1081,8 +1081,8 @@ static void ScaleARGB(const uint8* src, int src_stride,
     // Scale step for point sampling duplicates all pixels equally.
     dx = (Abs(src_width) << 16) / dst_width;
     dy = (src_height << 16) / dst_height;
-    x = (dx >= 65536) ? ((dx >> 1) - 32768) : (dx >> 1);
-    y = (dy >= 65536) ? ((dy >> 1) - 32768) : (dy >> 1);
+    x = dx >> 1;
+    y = dy >> 1;
   }
   // Negative src_width means horizontally mirror.
   if (src_width < 0) {