'**DESCRIPTION**
To set the region of interest.
**PARAMETERS**
* *roi* - tuple - It is a tuple of size 4. where region of interest is to the center of the screen.
**RETURNS**
None
**EXAMPLE**
>>> sc = ScreenCamera()
>>> res = sc.getResolution()
>>> sc.setROI(res[0]/4,res[1]/4,res[0]/2,res[1]/2)
>>> img = sc.getImage()
>>> s.show()'

def setROI(self, roi):

    if (isinstance(roi, tuple) and (len(roi) == 4)):
        self._roi = roi
    return
