NV12Scale function using split/merge on UV channal

Bug: libyuv:718, libyuv:838, b/168918847
Change-Id: I78b27baac50f0ce955e00cb6aaf7dfe5a0cb1e3d
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/2432067
Commit-Queue: Frank Barchard <fbarchard@chromium.org>
Reviewed-by: richard winterton <rrwinterton@gmail.com>

1 files changed, 64 insertions, 1 deletions

diff --git a/source/scale.cc b/source/scale.cc
index b17920a6..d26bfec7 100644
--- a/source/scale.cc
+++ b/source/scale.cc
@@ -1670,7 +1670,7 @@ void ScalePlane_16(const uint16_t* src,
   }
   if (dst_width == src_width && filtering != kFilterBox) {
     int dy = FixedDiv(src_height, dst_height);
-    // Arbitrary scale vertically, but unscaled vertically.
+    // Arbitrary scale vertically, but unscaled horizontally.
     ScalePlaneVertical_16(src_height, dst_width, dst_height, src_stride,
                           dst_stride, src, dst, 0, 0, dy, 1, filtering);
     return;
@@ -1869,6 +1869,69 @@ int I444Scale_16(const uint16_t* src_y,
   return 0;
 }
 
+// Scale an NV12 image.
+// This function in turn calls a scaling function for each plane.
+
+// TODO(https://bugs.chromium.org/p/libyuv/issues/detail?id=838): Remove
+// this once libyuv implements NV12Scale and use the libyuv::NV12Scale().
+// This is copy-pasted from
+// webrtc/common_video/libyuv/include/webrtc_libyuv.h
+int NV12Scale(const uint8_t* src_y,
+               int src_stride_y,
+               const uint8_t* src_uv,
+               int src_stride_uv,
+               int src_width,
+               int src_height,
+               uint8_t* dst_y,
+               int dst_stride_y,
+               uint8_t* dst_uv,
+               int dst_stride_uv,
+               int dst_width,
+               int dst_height,
+               enum FilterMode filtering) {
+  const int src_chroma_width = (src_width + 1) / 2;
+  const int src_chroma_height = (src_height + 1) / 2;
+
+  if (src_width == dst_width && src_height == dst_height) {
+    // No scaling.
+    libyuv::CopyPlane(src_y, src_stride_y, dst_y, dst_stride_y, src_width,
+                      src_height);
+    libyuv::CopyPlane(src_uv, src_stride_uv, dst_uv, dst_stride_uv,
+                      src_chroma_width * 2, src_chroma_height);
+    return 0;
+  }
+
+  // Scaling.
+  // Allocate temporary memory for spitting UV planes and scaling them.
+  const int dst_chroma_width = (dst_width + 1) / 2;
+  const int dst_chroma_height = (dst_height + 1) / 2;
+
+  align_buffer_64(tmp_buffer,
+  	              src_chroma_width * src_chroma_height * 2 +
+  	              dst_chroma_width * dst_chroma_height * 2);
+
+  uint8_t* const src_u = tmp_buffer;
+  uint8_t* const src_v = src_u + src_chroma_width * src_chroma_height;
+  uint8_t* const dst_u = src_v + src_chroma_width * src_chroma_height;
+  uint8_t* const dst_v = dst_u + dst_chroma_width * dst_chroma_height;
+
+  // Split source UV plane into separate U and V plane using the temporary data.
+  libyuv::SplitUVPlane(src_uv, src_stride_uv, src_u, src_chroma_width, src_v,
+                       src_chroma_width, src_chroma_width, src_chroma_height);
+
+  // Scale the planes.
+  libyuv::I420Scale(
+      src_y, src_stride_y, src_u, src_chroma_width, src_v, src_chroma_width,
+      src_width, src_height, dst_y, dst_stride_y, dst_u, dst_chroma_width,
+      dst_v, dst_chroma_width, dst_width, dst_height, filtering);
+
+  // Merge the UV planes into the destination.
+  libyuv::MergeUVPlane(dst_u, dst_chroma_width, dst_v, dst_chroma_width, dst_uv,
+                       dst_stride_uv, dst_chroma_width, dst_chroma_height);
+  free_aligned_buffer_64(tmp_buffer);
+  return 0;
+}
+
 // Deprecated api
 LIBYUV_API
 int Scale(const uint8_t* src_y,