Get RGB from a SurfaceView displaying Live camera

Question

I am displaying a live camera in SurfaceView using camera.startPreview();. Any idea on how I can get live RGB readings from the camera?

Thanks

Answer 1

I thought I could get the data converted from the SurfaceView. But the best method to use is :

• Set the camera's orientation to 90 degrees.
• Set output format to NV21 (which is guranteed to be supported on all devices).
• Set to turn the Flash ON.
• Start preview in the SurfaceView.

List item

camera = Camera.open();
cameraParam = camera.getParameters();
cameraParam.setPreviewFormat(ImageFormat.NV21);
camera.setDisplayOrientation(90);
camera.setParameters(cameraParam);
cameraParam = camera.getParameters();
camera.setPreviewDisplay(surfaceHolder);
cameraParam.setFlashMode(Parameters.FLASH_MODE_TORCH);
camera.setParameters(cameraParam);
camera.startPreview();

Then, I call the setPreviewCallback and onPreviewFrame to get the incoming frame, and convert it to RGB pixel array. Which I can then get intensity of each color in the picture by averaging all pixels intensity by running myPixels array through a for loop, and checking Color.red(myPixels[i]) for each desired color (inside the onPreviewFrame).

camera.setPreviewCallback(new PreviewCallback() {
    @Override
    public void onPreviewFrame(byte[] data, Camera camera) {
        int frameHeight = camera.getParameters().getPreviewSize().height;
        int frameWidth = camera.getParameters().getPreviewSize().width;
        // number of pixels//transforms NV21 pixel data into RGB pixels  
        int rgb[] = new int[frameWidth * frameHeight];
        // convertion
        int[] myPixels = decodeYUV420SP(rgb, data, frameWidth, frameHeight);
    }
}

Where decodeYUV420SP is found here.

I timed this operation to take about 200ms for each frame. Is there a faster way of doing it?

Answer 2

You can do similar something like below

camera.takePicture(shutterCallback, rawCallback, jpegCallback);

    jpegCallback = new PictureCallback() {
    public void onPictureTaken(byte[] data, Camera camera) {
        FileOutputStream outStream = null;
        try {
            Bitmap bitmap = BitmapFactory.decodeByteArray(data, offset, length);

         int[] pix = new int[picw * pich];
         bitmap.getPixels(pix, 0, picw, 0, 0, picw, pich);

         int R, G, B,Y;

         for (int y = 0; y < pich; y++){
         for (int x = 0; x < picw; x++)
             {
             int index = y * picw + x;
             int R = (pix[index] >> 16) & 0xff;     //bitwise shifting
             int G = (pix[index] >> 8) & 0xff;
             int B = pix[index] & 0xff;

             pix[index] = 0xff000000 | (R << 16) | (G << 8) | B;
             }}


        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
        }
     }
};

here camera.takePicture(shutterCallback, rawCallback, jpegCallback); method call on image capture time , so i think you need to do continually call this method while you camera is open .