Add alpha channel stride on CanvasCaptureHandler

This CL adds stride support for cases where canvas has aligned
alpha channel. Note that, this code is still temporary and will be
replaced by libyuv::ARGBToA when available.

BUG= 524218
TEST= http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=3905

Review URL: https://codereview.chromium.org/1826923002

Cr-Commit-Position: refs/heads/master@{#383017}

1 files changed, 29 insertions, 4 deletions

diff --git a/content/renderer/media/canvas_capture_handler.cc b/content/renderer/media/canvas_capture_handler.cc
index 6056712..e0d6089e 100644
--- a/content/renderer/media/canvas_capture_handler.cc
+++ b/content/renderer/media/canvas_capture_handler.cc
@@ -21,6 +21,32 @@
 #include "third_party/WebKit/public/platform/WebString.h"
 #include "third_party/libyuv/include/libyuv.h"
 
+namespace {
+
+static void CopyAlphaChannelIntoVideoFrame(
+    const uint8_t* const source,
+    const scoped_refptr<media::VideoFrame>& dest_frame) {
+  const gfx::Size& size = dest_frame->coded_size();
+  const int stride = dest_frame->stride(media::VideoFrame::kAPlane);
+
+  if (stride == size.width()) {
+    for (int p = 0; p < size.GetArea(); ++p)
+      dest_frame->data(media::VideoFrame::kAPlane)[p] = source[p * 4 + 3];
+    return;
+  }
+
+  // Copy apha values one-by-one if the destination stride != source width.
+  for (int h = 0; h < size.height(); ++h) {
+    const uint8_t* const src_ptr = &source[4 * h * size.width()];
+    uint8_t* dest_ptr =
+        &dest_frame->data(media::VideoFrame::kAPlane)[h * stride];
+    for (int pixel_index = 0; pixel_index < 4 * size.width(); pixel_index += 4)
+      *(dest_ptr++) = src_ptr[pixel_index + 3];
+  }
+}
+
+}  // namespace
+
 namespace content {
 
 // Implementation VideoCapturerSource that is owned by
@@ -203,8 +229,6 @@ void CanvasCaptureHandler::CreateNewFrame(const SkImage* image) {
       gfx::Rect(size), size, timestamp - base::TimeTicks());
   DCHECK(video_frame);
 
-  // TODO(emircan): Use https://code.google.com/p/libyuv/issues/detail?id=572
-  // when it becomes available.
   libyuv::ARGBToI420(temp_data_.data(), row_bytes_,
                      video_frame->data(media::VideoFrame::kYPlane),
                      video_frame->stride(media::VideoFrame::kYPlane),
@@ -214,8 +238,9 @@ void CanvasCaptureHandler::CreateNewFrame(const SkImage* image) {
                      video_frame->stride(media::VideoFrame::kVPlane),
                      size.width(), size.height());
   if (!isOpaque) {
-    for (int p = 0; p < size.GetArea(); ++p)
-      video_frame->data(media::VideoFrame::kAPlane)[p] = temp_data_[p * 4 + 3];
+    // TODO(emircan): Use https://code.google.com/p/libyuv/issues/detail?id=572
+    // when it becomes available.
+    CopyAlphaChannelIntoVideoFrame(temp_data_.data(), video_frame);
   }
 
   io_task_runner_->PostTask(