ImageCapture: Implement TakePhoto() for Linux/CrOs

media/capture/video/linux/v4l2_capture_delegate.cc

Index: media/capture/video/linux/v4l2_capture_delegate.cc
diff --git a/media/capture/video/linux/v4l2_capture_delegate.cc b/media/capture/video/linux/v4l2_capture_delegate.cc
index a6f47b551ed410f3fa28c5f45b888eee6f97c0b7..491f4f869281c3a343bb47c53995af9c0b7a6ca4 100644
--- a/media/capture/video/linux/v4l2_capture_delegate.cc
+++ b/media/capture/video/linux/v4l2_capture_delegate.cc
@@ -321,6 +321,12 @@ void V4L2CaptureDelegate::StopAndDeAllocate() {
   client_.reset();
 }
 
+void V4L2CaptureDelegate::TakePhoto(
+    VideoCaptureDevice::TakePhotoCallback callback) {
+  take_photo_callbacks_.push(std::move(callback));

[mcasas, 2016/09/16 03:50:36]

nit: add
DCHECK(v4l2_task_runner_->BelongsToCurrentThread());

[xianglu, 2016/09/16 18:22:33]

Done.

+  DVLOG(1) << "in V4L2CaptureDelegate: callback moved";

[mcasas, 2016/09/16 03:50:36]

nit: remove DVLOG()s when you submit for review,

[xianglu, 2016/09/16 18:22:33]

Done.

+}
+
 void V4L2CaptureDelegate::SetRotation(int rotation) {
   DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
   DCHECK(rotation >= 0 && rotation < 360 && rotation % 90 == 0);
@@ -401,6 +407,18 @@ void V4L2CaptureDelegate::DoCapture() {
         buffer_tracker->start(), buffer_tracker->payload_size(),
         capture_format_, rotation_, base::TimeTicks::Now(), timestamp);
 
+    // Process all the callbacks from TakePhoto()

[mcasas, 2016/09/16 03:50:36]

nit: No need for this comment.

[xianglu, 2016/09/16 18:22:33]

Done.

+    while (!take_photo_callbacks_.empty()) {
+      VideoCaptureDevice::TakePhotoCallback cb =
+          std::move(take_photo_callbacks_.front());
+      take_photo_callbacks_.pop();
+
+      if (mojom::BlobPtr blob = GetPhotoBlob(buffer_tracker, buffer))

[mcasas, 2016/09/16 03:50:36]

nit: Don't mix assignments and conditionals.

[xianglu, 2016/09/16 18:22:33]

Done.

+        cb.Run(std::move(blob));
+      else
+        DVLOG(3) << "blob pointer is null.";
+    }
+
     if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QBUF, &buffer)) < 0) {
       SetErrorState(FROM_HERE, "Failed to enqueue capture buffer");
       return;
@@ -411,6 +429,60 @@ void V4L2CaptureDelegate::DoCapture() {
       FROM_HERE, base::Bind(&V4L2CaptureDelegate::DoCapture, this));
 }
 
+mojom::BlobPtr V4L2CaptureDelegate::GetPhotoBlob(
+    const scoped_refptr<BufferTracker>& buffer_tracker,
+    const v4l2_buffer& buffer) {
+  std::unique_ptr<uint8_t[]> dst_argb(new uint8_t[VideoFrame::AllocationSize(
+      PIXEL_FORMAT_ARGB, capture_format_.frame_size)]);
+  mojom::BlobPtr blob = mojom::Blob::New();
+
+  DVLOG(1) << "Format captured: "
+           << VideoPixelFormatToString(capture_format_.pixel_format);
+
+  uint32 src_format;
+  switch (capture_format_.pixel_format) {
+    case VideoPixelFormat::PIXEL_FORMAT_MJPEG:
+      blob->data.resize(buffer.bytesused);

[mcasas, 2016/09/16 03:50:36]

If we take this path, |dst_argb| would be unused and
we'll be bashing memory. Instead, try to allocate as
close as possible to the use, and not allocate what
you might not need (lazy developer). E.g.:

mojom::BlobPtr V4L2CaptureDelegate::GetPhotoBlob(
    const scoped_refptr<BufferTracker>& buffer_tracker,
    const v4l2_buffer& buffer) {

  uint32 src_format;
  switch (capture_format_.pixel_format) {
    case VideoPixelFormat::PIXEL_FORMAT_MJPEG:
      mojom::BlobPtr blob = mojom::Blob::New();
      blob->data.resize(buffer.bytesused);
      memcpy(blob->data.data(), buffer_tracker->start(), buffer.bytesused);
      blob->mime_type = "image/jpeg";
      return blob;
    case VideoPixelFormat::PIXEL_FORMAT_UYVY:
      src_format = libyuv::FOURCC_UYVY;
      break;
    case VideoPixelFormat::PIXEL_FORMAT_YUY2:
      src_format = libyuv::FOURCC_YUY2;
      break;
    default:
      DVLOG(3) << "FORMAT not supported.";
      return nullptr;
  }

  std::unique_ptr<uint8_t[]> dst_argb(new uint8_t[VideoFrame::AllocationSize(
      PIXEL_FORMAT_ARGB, capture_format_.frame_size)]);
  if (ConvertToARGB(...) {

  }

  mojom::BlobPtr blob = mojom::Blob::New();
  const bool result = gfx::PNGCodec::Encode(...)

}

[xianglu, 2016/09/16 18:22:33]

Indeed. Should work this way.

+      memcpy(blob->data.data(), buffer_tracker->start(), buffer.bytesused);
+      blob->mime_type = "image/jpeg";
+      return blob;
+    case VideoPixelFormat::PIXEL_FORMAT_UYVY:
+      src_format = libyuv::FOURCC_UYVY;
+      break;
+    case VideoPixelFormat::PIXEL_FORMAT_YUY2:
+      src_format = libyuv::FOURCC_YUY2;
+      break;
+    default:
+      DVLOG(3) << "FORMAT not supported.";

[mcasas, 2016/09/16 03:50:36]

Instead of DVLOG(3), consider using

DLOG(ERROR) << VideoPixelFormatToString(capture_format_.pixel_format);

Which better conveys meaning. This also applies
to l.467, although I would remove that log.

[xianglu, 2016/09/16 18:22:33]

Why would you remove ConvertFailure log?

[mcasas, 2016/09/16 18:59:15]

All those error logs are only really useful for 
developers/development; IOW there's a 
realistic possibility that the other formats
would be hit, but what's this error going to 
tell you that you don't know already? Returning 
nullptr will make takePhoto() fail ultimately.

+      return nullptr;
+  }
+
+  if (ConvertToARGB(buffer_tracker->start(), buffer.bytesused, dst_argb.get(),
+                    capture_format_.frame_size.width() * 4, 0 /* crop_x_pos */,
+                    0 /* crop_y_pos */, capture_format_.frame_size.width(),
+                    capture_format_.frame_size.height(),
+                    capture_format_.frame_size.width(),
+                    capture_format_.frame_size.height(),
+                    libyuv::RotationMode::kRotate0, src_format) != 0) {
+    DVLOG(3) << "Failed to convert buffer's pixel format from "
+             << VideoPixelFormatToString(capture_format_.pixel_format)
+             << " to ARGB";
+    return nullptr;
+  }
+
+  const gfx::PNGCodec::ColorFormat codec_color_format =
+      (kN32_SkColorType == kRGBA_8888_SkColorType) ? gfx::PNGCodec::FORMAT_RGBA
+                                                   : gfx::PNGCodec::FORMAT_BGRA;
+  const bool result = gfx::PNGCodec::Encode(
+      dst_argb.get(), codec_color_format, capture_format_.frame_size,
+      capture_format_.frame_size.width() * 4, true /* discard_transparency */,
+      std::vector<gfx::PNGCodec::Comment>(), &blob->data);
+  DCHECK(result);
+
+  blob->mime_type = "image/png";
+  return blob;
+}
+
 void V4L2CaptureDelegate::SetErrorState(
     const tracked_objects::Location& from_here,
     const std::string& reason) {