Add still image capture interface for VideoCaptureDevice.

media/video/capture/video_capture_device.h

 // 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.
 //
 // VideoCaptureDevice is the abstract base class for realizing video capture
 // device support in Chromium. It provides the interface for OS dependent
 // implementations.
 // The class is created and functions are invoked on a thread owned by
 // VideoCaptureManager. Capturing is done on other threads, depending on the OS
 // specific implementation.
@@ skipping 198 matching lines @@
         const VideoCaptureFormat& buffer_format,
         const scoped_refptr<media::VideoFrame>& frame,
         base::TimeTicks timestamp) = 0;
 
     // An error has occurred that cannot be handled and VideoCaptureDevice must
     // be StopAndDeAllocate()-ed. |reason| is a text description of the error.
     virtual void OnError(const std::string& reason) = 0;
 
     // VideoCaptureDevice requests the |message| to be logged.
     virtual void OnLog(const std::string& message) {}
+
+    // The video stream is being muted. After this callback, no more

[wuchengli, 2014/09/09 05:53:22]

s/is being/has/

[Owen Lin, 2014/09/11 06:17:59]

Done.

+    // OnIncomingCapturedData() will be called.

[wuchengli, 2014/09/09 05:53:21]

Explain OnMute and OnUnmute are called when image capture is started and ended
is called.

[Owen Lin, 2014/09/11 06:17:59]

Done.

+    virtual void OnMute() {}
+
+    // The video stream is being resumed.

[wuchengli, 2014/09/09 05:53:22]

s/is being/has/

[Owen Lin, 2014/09/11 06:18:00]

Done.

+    virtual void OnUnmute() {}
+  };
+
+  class MEDIA_EXPORT ImageClient {
+   public:
+    virtual ~ImageClient() {}
+
+    // Callback function to notify the client the caputred image is available.
+    virtual void OnIncomingCapturedData(const uint8* data,
+                                        int length,
+                                        const ImageCaptureFormat& format,
+                                        int rotation,
+                                        base::TimeTicks timestamp) = 0;
+
+    // Callback function to notify client the failure of the image capturing.
+    // The VideoCaptureDevice must be StopAndDeAllocate()-ed. |reason| is a

[wuchengli, 2014/09/09 05:53:22]

s/StopAndDeAllocate/CloseImageCapture/

[Owen Lin, 2014/09/11 06:17:59]

I do mean StopAndDeallocate. In the current implementation, the device would go
to an error state and has to be restart again. No error is expected so I don't
think we need to spend too much effort in resuming from the error state for
still image capture.

+    // text description of the error.
+    virtual void OnError(const std::string& reason) = 0;
   };
 
   // Creates a VideoCaptureDevice object.
   // Return NULL if the hardware is not available.
   static VideoCaptureDevice* Create(
       scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
       const Name& device_name);
   virtual ~VideoCaptureDevice();
 
   // Gets the names of all video capture devices connected to this computer.
   static void GetDeviceNames(Names* device_names);
 
   // Gets the supported formats of a particular device attached to the system.
   // This method should be called before allocating or starting a device. In
   // case format enumeration is not supported, or there was a problem, the
   // formats array will be empty.
   static void GetDeviceSupportedFormats(const Name& device,
                                         VideoCaptureFormats* supported_formats);
 
+  // Gets the supported formats for still image of a particular device attached
+  // to the system.
+  static void GetDeviceSupportedImageFormats(
+      const Name& device,
+      ImageCaptureFormats* supported_formats);
+
   // Prepares the camera for use. After this function has been called no other
   // applications can use the camera. StopAndDeAllocate() must be called before
   // the object is deleted.
   virtual void AllocateAndStart(const VideoCaptureParams& params,
                                 scoped_ptr<Client> client) = 0;
 
   // Deallocates the camera, possibly asynchronously.
   //
   // This call requires the device to do the following things, eventually: put
   // camera hardware into a state where other applications could use it, free
   // the memory associated with capture, and delete the |client| pointer passed
   // into AllocateAndStart.
   //
   // If deallocation is done asynchronously, then the device implementation must
   // ensure that a subsequent AllocateAndStart() operation targeting the same ID
   // would be sequenced through the same task runner, so that deallocation
   // happens first.
   virtual void StopAndDeAllocate() = 0;
 
   // Gets the power line frequency from the current system time zone if this is
   // defined, otherwise returns 0.
   int GetPowerLineFrequencyForLocation() const;
 
+  // Initializes the device for still image capture for the given image format.
+  // This function is used to allocate resources.

[wuchengli, 2014/09/09 05:53:22]

Does the caller require to start the video stream first to use image capture?

[Owen Lin, 2014/09/11 06:17:59]

Yes. Comment added.

+  virtual void InitializeImageCapture(const ImageCaptureFormat& image_format,

[wuchengli, 2014/09/09 05:53:22]

Using AllocateImageCapture and DeAllocateImageCapture is more consistent?

[Owen Lin, 2014/09/11 06:17:59]

The problem is we may not really allocate resources here (like the current
implementation).

+                                      scoped_ptr<ImageClient> client);
+
+  // Releases used resources for image capture.

[wuchengli, 2014/09/09 05:53:22]

s/used//

Does CloseImageCapture have to be called before the object is deleted like
StopAndDeAllocate? Or the destructor handles it?

[Owen Lin, 2014/09/11 06:18:00]

Command added. It has to be called before StopAndDeAllocate().

+  virtual void CloseImageCapture() {}
+
+  // Gets one image from the device. It will returne the picture by the

[wuchengli, 2014/09/09 05:53:21]

s/returne/return/. s/picture/image/.

[Owen Lin, 2014/09/11 06:18:00]

Done.

+  // ImageClient's OnIncomingCapturedData() callback.

[wuchengli, 2014/09/09 05:53:21]

ImageClient::OnIncomingCapturedData(). Also mention OnMute and OnUnmute will be
called.

[Owen Lin, 2014/09/11 06:17:59]

Done.

+  //
+  // This function must be called between InitializeImageCapture() and
+  // CloseImageCapture().
+  virtual void CaptureImage() {}
+
  protected:
   static const int kPowerLine50Hz = 50;
   static const int kPowerLine60Hz = 60;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_