Crop image ala Google Goggles

I'm开发者_如何学JAVA trying to do some ROI (region of interest) selection in my app, but I don´t know, how to create some kind of resizable (by fingers) rectangle like you can see in Google Goggles. Can you help me? Is there any source code example?

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My final solution is to draw and rectangle in the midle of a view and implement onTouchEvent() in my activity to set new corners coordinates like this:

@Override
public boolean onTouchEvent(MotionEvent me) {
    if(SETTING_ROI == true){
        if (me.getAction() == MotionEvent.ACTION_DOWN) {
            START_DRAGGING = true;
            myView.selectCorner((int) me.getRawX(), (int) me.getRawY()); // selecst nearest corner
        }
        if (me.getAction() == MotionEvent.ACTION_MOVE){
            Log.d(TAG, "ACTION_MOVE");
            myView.moveCorner((int) me.getRawX(), (int) me.getRawY()); // move selected corner continuously
        }
        if (me.getAction() == MotionEvent.ACTION_UP){
            if (START_DRAGGING == true) {
                START_DRAGGING = false;
                myView.moveCorner((int) me.getRawX(), (int) me.getRawY()); // final selected corner move
            }
        }
    }
    return false;
}

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Could you reuse code from the Gallery-Cropper?

The CropImage class source code is available here.