From aae7deb5cf7269144e04045d3e0fa05054759dbe Mon Sep 17 00:00:00 2001
From: "fbarchard@google.com"
 <fbarchard@google.com@16f28f9a-4ce2-e073-06de-1de4eb20be90>
Date: Sat, 7 Dec 2013 00:55:23 +0000
Subject: [PATCH] yuv use scale slope calc BUG=none TEST=drmem
 R=tpsiaki@google.com

Review URL: https://webrtc-codereview.appspot.com/5319004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@899 16f28f9a-4ce2-e073-06de-1de4eb20be90
---
 include/libyuv/scale.h     |  2 +-
 source/planar_functions.cc |  8 +++-
 source/scale.cc            | 95 ++++++++++----------------------------
 source/scale_common.cc     |  2 +-
 4 files changed, 34 insertions(+), 73 deletions(-)

diff --git a/include/libyuv/scale.h b/include/libyuv/scale.h
index 3bfddb29d..b672dbfce 100644
--- a/include/libyuv/scale.h
+++ b/include/libyuv/scale.h
@@ -21,7 +21,7 @@ extern "C" {
 // Supported filtering.
 enum FilterMode {
   kFilterNone = 0,  // Point sample; Fastest.
-  kFilterLinear = 1, // Filter horizontally only.
+  kFilterLinear = 1,  // Filter horizontally only.
   kFilterBilinear = 2,  // Faster than box, but lower quality scaling down.
   kFilterBox = 3  // Highest quality.
 };
diff --git a/source/planar_functions.cc b/source/planar_functions.cc
index 7d3cfa9ce..114faaef6 100644
--- a/source/planar_functions.cc
+++ b/source/planar_functions.cc
@@ -172,10 +172,16 @@ int I420ToI400(const uint8* src_y, int src_stride_y,
   return 0;
 }
 
-// Mirror a plane of data
+// Mirror a plane of data.
 void MirrorPlane(const uint8* src_y, int src_stride_y,
                  uint8* dst_y, int dst_stride_y,
                  int width, int height) {
+  // Negative height means invert the image.
+  if (height < 0) {
+    height = -height;
+    src_y = src_y + (height - 1) * src_stride_y;
+    src_stride_y = -src_stride_y;
+  }
   void (*MirrorRow)(const uint8* src, uint8* dst, int width) = MirrorRow_C;
 #if defined(HAS_MIRRORROW_NEON)
   if (TestCpuFlag(kCpuHasNEON) && IS_ALIGNED(width, 16)) {
diff --git a/source/scale.cc b/source/scale.cc
index f9ca3bf44..e48d80cfa 100644
--- a/source/scale.cc
+++ b/source/scale.cc
@@ -382,16 +382,14 @@ static void ScalePlaneBox(int src_width, int src_height,
                           const uint8* src_ptr, uint8* dst_ptr) {
   assert(dst_width > 0);
   assert(dst_height > 0);
-  int dx = FixedDiv(Abs(src_width), dst_width);
-  int dy = FixedDiv(src_height, dst_height);
+
+  // Initial source x/y coordinate and step values as 16.16 fixed point.
   int x = 0;
   int y = 0;
-  // Negative src_width means horizontally mirror.
-  if (src_width < 0) {
-    x += (dst_width - 1) * dx;
-    dx = -dx;
-    src_width = -src_width;
-  }
+  int dx = 0;
+  int dy = 0;
+  ScaleSlope(src_width, src_height, dst_width, dst_height, kFilterBox,
+             &x, &y, &dx, &dy);
   const int max_y = (src_height << 16);
   if (!IS_ALIGNED(src_width, 16) || (src_width > kMaxStride) ||
       dst_height * 2 > src_height) {
@@ -457,6 +455,14 @@ void ScalePlaneBilinearDown(int src_width, int src_height,
   assert(dst_height > 0);
   assert(Abs(src_width) <= kMaxStride);
 
+  // Initial source x/y coordinate and step values as 16.16 fixed point.
+  int x = 0;
+  int y = 0;
+  int dx = 0;
+  int dy = 0;
+  ScaleSlope(src_width, src_height, dst_width, dst_height, filtering,
+             &x, &y, &dx, &dy);
+
   SIMD_ALIGNED(uint8 row[kMaxStride + 16]);
 
   void (*InterpolateRow)(uint8* dst_ptr, const uint8* src_ptr,
@@ -517,28 +523,6 @@ void ScalePlaneBilinearDown(int src_width, int src_height,
   }
 #endif
 
-  int dx = 0;
-  int dy = 0;
-  int x = 0;
-  int y = 0;
-  if (dst_width <= Abs(src_width)) {
-    dx = FixedDiv(Abs(src_width), dst_width);
-    x = (dx >> 1) - 32768;
-  } else if (dst_width > 1) {
-    dx = FixedDiv(Abs(src_width) - 1, dst_width - 1);
-  }
-  // Negative src_width means horizontally mirror.
-  if (src_width < 0) {
-    x += (dst_width - 1) * dx;
-    dx = -dx;
-    src_width = -src_width;
-  }
-  if (dst_height <= src_height) {
-    dy = FixedDiv(src_height, dst_height);
-    y = (dy >> 1) - 32768;
-  } else if (dst_height > 1) {
-    dy = FixedDiv(src_height - 1, dst_height - 1);
-  }
   const int max_y = (src_height - 1) << 16;
   for (int j = 0; j < dst_height; ++j) {
     if (y > max_y) {
@@ -570,28 +554,14 @@ void ScalePlaneBilinearUp(int src_width, int src_height,
   assert(dst_width > 0);
   assert(dst_height > 0);
   assert(Abs(dst_width) <= kMaxStride);
-  int dx = 0;
-  int dy = 0;
+
+  // Initial source x/y coordinate and step values as 16.16 fixed point.
   int x = 0;
   int y = 0;
-  if (dst_width <= Abs(src_width)) {
-    dx = FixedDiv(Abs(src_width), dst_width);
-    x = (dx >> 1) - 32768;
-  } else if (dst_width > 1) {
-    dx = FixedDiv(Abs(src_width) - 1, dst_width - 1);
-  }
-  // Negative src_width means horizontally mirror.
-  if (src_width < 0) {
-    x += (dst_width - 1) * dx;
-    dx = -dx;
-    src_width = -src_width;
-  }
-  if (dst_height <= src_height) {
-    dy = FixedDiv(src_height, dst_height);
-    y = (dy >> 1) - 32768;
-  } else if (dst_height > 1) {
-    dy = FixedDiv(src_height - 1, dst_height - 1);
-  }
+  int dx = 0;
+  int dy = 0;
+  ScaleSlope(src_width, src_height, dst_width, dst_height, filtering,
+             &x, &y, &dx, &dy);
 
   void (*InterpolateRow)(uint8* dst_ptr, const uint8* src_ptr,
       ptrdiff_t src_stride, int dst_width, int source_y_fraction) =
@@ -715,28 +685,13 @@ static void ScalePlaneSimple(int src_width, int src_height,
                              int dst_width, int dst_height,
                              int src_stride, int dst_stride,
                              const uint8* src_ptr, uint8* dst_ptr) {
-  int dx = 0;
-  int dy = 0;
+  // Initial source x/y coordinate and step values as 16.16 fixed point.
   int x = 0;
   int y = 0;
-  if (dst_width <= Abs(src_width)) {
-    dx = FixedDiv(Abs(src_width), dst_width);
-    x = (dx >> 1) - 32768;
-  } else if (dst_width > 1) {
-    dx = FixedDiv(Abs(src_width) - 1, dst_width - 1);
-  }
-  // Negative src_width means horizontally mirror.
-  if (src_width < 0) {
-    x += (dst_width - 1) * dx;
-    dx = -dx;
-    src_width = -src_width;
-  }
-  if (dst_height <= src_height) {
-    dy = FixedDiv(src_height, dst_height);
-    y = (dy >> 1) - 32768;
-  } else if (dst_height > 1) {
-    dy = FixedDiv(src_height - 1, dst_height - 1);
-  }
+  int dx = 0;
+  int dy = 0;
+  ScaleSlope(src_width, src_height, dst_width, dst_height, kFilterNone,
+             &x, &y, &dx, &dy);
 
   void (*ScaleCols)(uint8* dst_ptr, const uint8* src_ptr,
       int dst_width, int x, int dx) = ScaleCols_C;
diff --git a/source/scale_common.cc b/source/scale_common.cc
index 468aaa267..b0ba1e846 100644
--- a/source/scale_common.cc
+++ b/source/scale_common.cc
@@ -613,7 +613,7 @@ void ScaleSlope(int src_width, int src_height,
     }
     if (dst_height <= src_height) {
       *dy = FixedDiv(src_height,  dst_height);
-      *y = CENTERSTART(*dy, -32768);
+      *y = CENTERSTART(*dy, -32768);  // 32768 = -0.5 to center bilinear.
     } else if (dst_height > 1) {
       *dy = FIXEDDIV1(src_height, dst_height);
       *y = 0;