'Return the extent as a 4-tuple (xmin, ymin, xmax, ymax).'

@property
def extent(self):

    xval = (self.origin.x + (self.scale.x * self.width))
    yval = (self.origin.y + (self.scale.y * self.height))
    xmin = min(xval, self.origin.x)
    xmax = max(xval, self.origin.x)
    ymin = min(yval, self.origin.y)
    ymax = max(yval, self.origin.y)
    return (xmin, ymin, xmax, ymax)
