Handle Alpha channel in Canvas capture

media/base/video_util.cc

 // Copyright (c) 2012 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 "media/base/video_util.h"
 
 #include <cmath>
 
 #include "base/logging.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/numerics/safe_math.h"
 #include "media/base/video_frame.h"
 #include "media/base/yuv_convert.h"
 
 namespace media {
 
+namespace {
+
+// Empty method used for keeping a reference to the original media::VideoFrame.
+// The reference to |frame| is kept in the closure that calls this method.

[mcasas, 2016/02/29 23:48:01]

nit: This second sentence doesn't make sense :)

[emircan, 2016/03/01 20:07:55]

Done.

+void ReleaseOriginalFrame(const scoped_refptr<media::VideoFrame>& frame) {}

[mcasas, 2016/02/29 23:48:01]

Can we use base::DeletePointer? [1]

Also, no empty line 22.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/base/bind_helpers....

[emircan, 2016/03/01 20:07:55]

DeletePointer doesn't support ref_ptr as it only expects a naked ptr. Also, the
space is for the namespace. 

+
+}  // namespace
+
 gfx::Size GetNaturalSize(const gfx::Size& visible_size,
                          int aspect_ratio_numerator,
                          int aspect_ratio_denominator) {
   if (aspect_ratio_denominator == 0 ||
       aspect_ratio_numerator < 0 ||
       aspect_ratio_denominator < 0)
     return gfx::Size();
 
   double aspect_ratio = aspect_ratio_numerator /
       static_cast<double>(aspect_ratio_denominator);
@@ skipping 282 matching lines @@
                     frame->data(kY) + y_offset,
                     frame->data(kU) + uv_offset,
                     frame->data(kV) + uv_offset,
                     region_in_frame.width(),
                     region_in_frame.height(),
                     stride,
                     frame->stride(kY),
                     uv_stride);
 }
 
+scoped_refptr<VideoFrame> DropYV12AAlphaChannel(
+    const scoped_refptr<VideoFrame>& frame) {
+  DCHECK_EQ(VideoFrame::STORAGE_OWNED_MEMORY, frame->storage_type());
+  DCHECK_EQ(PIXEL_FORMAT_YV12A, frame->format());
+
+  scoped_refptr<media::VideoFrame> wrapped_frame =
+      media::VideoFrame::WrapVideoFrame(frame, PIXEL_FORMAT_I420,
+                                        frame->visible_rect(),
+                                        frame->natural_size());
+  if (!wrapped_frame)
+    return nullptr;
+  wrapped_frame->AddDestructionObserver(
+      base::Bind(&ReleaseOriginalFrame, frame));
+  return wrapped_frame;
+}
+
 }  // namespace media