Treat YU12 as an alias for I420. Simplify setting of inv_crop_height.

source/convert_to_i420.cc

 /*
  *  Copyright 2011 The LibYuv Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS. All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 21 matching lines @@
                   uint8* v, int v_stride,
                   int crop_x, int crop_y,
                   int src_width, int src_height,
                   int crop_width, int crop_height,
                   enum RotationMode rotation,
                   uint32 fourcc) {
   uint32 format = CanonicalFourCC(fourcc);
   int aligned_src_width = (src_width + 1) & ~1;
   const uint8* src;
   const uint8* src_uv;
-  int abs_src_height = (src_height < 0) ? -src_height : src_height;
-  int inv_crop_height = (crop_height < 0) ? -crop_height : crop_height;
+  const int abs_src_height = (src_height < 0) ? -src_height : src_height;
+  // TODO(nisse): Why allow crop_height < 0?
+  const int abs_crop_height = (crop_height < 0) ? -crop_height : crop_height;
   int r = 0;
   LIBYUV_BOOL need_buf = (rotation && format != FOURCC_I420 &&
       format != FOURCC_NV12 && format != FOURCC_NV21 &&
-      format != FOURCC_YU12 && format != FOURCC_YV12) || y == sample;
+      format != FOURCC_YV12) || y == sample;
   uint8* tmp_y = y;
   uint8* tmp_u = u;
   uint8* tmp_v = v;
   int tmp_y_stride = y_stride;
   int tmp_u_stride = u_stride;
   int tmp_v_stride = v_stride;
   uint8* rotate_buffer = NULL;
-  int abs_crop_height = (crop_height < 0) ? -crop_height : crop_height;
+  const int inv_crop_height =
+      (src_height < 0) ? -abs_crop_height : abs_crop_height;
 
   if (!y || !u || !v || !sample ||
       src_width <= 0 || crop_width <= 0  ||
       src_height == 0 || crop_height == 0) {
     return -1;
   }
-  if (src_height < 0) {
-    inv_crop_height = -inv_crop_height;
-  }
 
   // One pass rotation is available for some formats. For the rest, convert
   // to I420 (with optional vertical flipping) into a temporary I420 buffer,
   // and then rotate the I420 to the final destination buffer.
   // For in-place conversion, if destination y is same as source sample,
   // also enable temporary buffer.
   if (need_buf) {
     int y_size = crop_width * abs_crop_height;
     int uv_size = ((crop_width + 1) / 2) * ((abs_crop_height + 1) / 2);
     rotate_buffer = (uint8*)malloc(y_size + uv_size * 2);
@@ skipping 132 matching lines @@
     case FOURCC_M420:
       src = sample + (src_width * crop_y) * 12 / 8 + crop_x;
       r = M420ToI420(src, src_width,
                      y, y_stride,
                      u, u_stride,
                      v, v_stride,
                      crop_width, inv_crop_height);
       break;
     // Triplanar formats
     case FOURCC_I420:
-    case FOURCC_YU12:
     case FOURCC_YV12: {
       const uint8* src_y = sample + (src_width * crop_y + crop_x);
       const uint8* src_u;
       const uint8* src_v;
       int halfwidth = (src_width + 1) / 2;
       int halfheight = (abs_src_height + 1) / 2;
       if (format == FOURCC_YV12) {
         src_v = sample + src_width * abs_src_height +
             (halfwidth * crop_y + crop_x) / 2;
         src_u = sample + src_width * abs_src_height +
@@ skipping 102 matching lines @@
     free(rotate_buffer);
   }
 
   return r;
 }
 
 #ifdef __cplusplus
 }  // extern "C"
 }  // namespace libyuv
 #endif