MediaStream Image Capture (2): Platform::ImageCaptureFrameGrabber and grabFrame()

content/renderer/media/image_capture_frame_grabber.cc

+// Copyright 2016 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 "content/renderer/media/image_capture_frame_grabber.h"
+
+#include "media/base/bind_to_current_loop.h"
+#include "media/base/video_frame.h"
+#include "media/base/video_util.h"
+#include "skia/ext/platform_canvas.h"
+#include "third_party/WebKit/public/platform/WebCallbacks.h"
+#include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
+#include "third_party/WebKit/public/platform/WebMediaStreamTrack.h"
+#include "third_party/libyuv/include/libyuv.h"
+#include "third_party/skia/include/core/SkImage.h"
+#include "third_party/skia/include/core/SkSurface.h"
+
+namespace content {
+
+using blink::WebImageCaptureGrabFrameCallbacks;
+
+namespace {
+
+void OnError(std::unique_ptr<WebImageCaptureGrabFrameCallbacks> callbacks) {
+  callbacks->onError();
+}
+
+// This internal method receives a |frame| and converts its pixels into a
+// SkImage via an internal SkSurface and SkPixmap. Alpha channel, if any, is
+// copied.
+void OnVideoFrame(const ImageCaptureFrameGrabber::SkImageDeliverCB& callback,
+                  const scoped_refptr<media::VideoFrame>& frame,
+                  base::TimeTicks /* current_time */) {
+  DCHECK(frame->format() == media::PIXEL_FORMAT_YV12 ||
+         frame->format() == media::PIXEL_FORMAT_I420 ||
+         frame->format() == media::PIXEL_FORMAT_YV12A);
+
+  const SkAlphaType alpha = media::IsOpaque(frame->format())
+                                ? kOpaque_SkAlphaType
+                                : kPremul_SkAlphaType;
+  const SkImageInfo info = SkImageInfo::MakeN32(
+      frame->visible_rect().width(), frame->visible_rect().height(), alpha);
+
+  sk_sp<SkSurface> surface = SkSurface::MakeRaster(info);
+  DCHECK(surface);
+
+  SkPixmap pixmap;
+  if (!skia::GetWritablePixels(surface->getCanvas(), &pixmap)) {
+    DLOG(ERROR) << "Error trying to map SkSurface's pixels";
+    callback.Run(sk_sp<SkImage>());
+    return;
+  }
+
+  libyuv::I420ToARGB(frame->visible_data(media::VideoFrame::kYPlane),
+                     frame->stride(media::VideoFrame::kYPlane),
+                     frame->visible_data(media::VideoFrame::kUPlane),
+                     frame->stride(media::VideoFrame::kUPlane),
+                     frame->visible_data(media::VideoFrame::kVPlane),
+                     frame->stride(media::VideoFrame::kVPlane),
+                     static_cast<uint8*>(pixmap.writable_addr()),
+                     pixmap.width() * 4, pixmap.width(), pixmap.height());
+
+  if (frame->format() == media::PIXEL_FORMAT_YV12A) {
+    DCHECK(!info.isOpaque());
+    // This function copies any plane into the alpha channel of an ARGB image.
+    libyuv::ARGBCopyYToAlpha(frame->visible_data(media::VideoFrame::kAPlane),
+                             frame->stride(media::VideoFrame::kAPlane),
+                             static_cast<uint8*>(pixmap.writable_addr()),
+                             pixmap.width() * 4, pixmap.width(),
+                             pixmap.height());
+  }
+
+  callback.Run(surface->makeImageSnapshot());
+}
+
+}  // anonymous namespace
+
+ImageCaptureFrameGrabber::ImageCaptureFrameGrabber() : weak_factory_(this) {}
+
+ImageCaptureFrameGrabber::~ImageCaptureFrameGrabber() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
+
+void ImageCaptureFrameGrabber::grabFrame(
+    blink::WebMediaStreamTrack* track,
+    WebImageCaptureGrabFrameCallbacks* callbacks) {
+  DVLOG(1) << __FUNCTION__;
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(!!callbacks);
+
+  DCHECK(track && !track->isNull() && track->getExtraData());
+  DCHECK_EQ(blink::WebMediaStreamSource::TypeVideo, track->source().getType());
+
+  ScopedWebCallbacks<WebImageCaptureGrabFrameCallbacks> scoped_callbacks =
+      make_scoped_web_callbacks(callbacks, base::Bind(&OnError));
+
+  // ConnectToTrack() must happen on render's Main Thread, whereas VideoFrames
+  // are delivered on a background thread though, so we Bind the callback to our
+  // current thread.
+  MediaStreamVideoSink::ConnectToTrack(
+      *track,
+      base::Bind(&OnVideoFrame, media::BindToCurrentLoop(base::Bind(
+                                    &ImageCaptureFrameGrabber::OnSkImage,
+                                    weak_factory_.GetWeakPtr(),
+                                    base::Passed(&scoped_callbacks)))));
+}
+
+void ImageCaptureFrameGrabber::OnSkImage(
+    ScopedWebCallbacks<WebImageCaptureGrabFrameCallbacks> callbacks,
+    sk_sp<SkImage> image) {
+  DVLOG(1) << __FUNCTION__;
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  MediaStreamVideoSink::DisconnectFromTrack();
+  if (image)
+    callbacks.PassCallbacks()->onSuccess(image);
+  else
+    callbacks.PassCallbacks()->onError();
+}
+
+}  // namespace content