def levels(self):
        
        """Returns a histogram for each RGBA channel.
        
        Returns a 4-tuple of lists, r, g, b, and a.
        Each list has 255 items, a count for each pixel value.
                
        """
        
        h = self.img.histogram()
        r = h[0:255]
        g = h[256:511]
        b = h[512:767]
        a = h[768:1024]
        
        return r, g, b, a
def levels(self):
        
        """Returns a histogram for each RGBA channel.
        
        Returns a 4-tuple of lists, r, g, b, and a.
        Each list has 255 items, a count for each pixel value.
                
        """
        
        h = self.img.histogram()
        r = h[0:255]
        g = h[256:511]
        b = h[512:767]
        a = h[768:1024]
        
        return r, g, b, a
Returns a histogram for each RGBA channel.
        
        Returns a 4-tuple of lists, r, g, b, and a.
        Each list has 255 items, a count for each pixel value.