def _on_mouse_down(self, event):
    ' if mouse clicked on crop area, allow moving crop '
    if ((event.x >= self.box[0]) and (event.x <= self.box[2])):
        if ((event.y >= self.box[1]) and (event.y <= self.box[3])):
            self.movingCrop = True
            self.lastLocation = [event.x, event.y]
if mouse clicked on crop area, allow moving crop
def _on_mouse_down(self, event):
    '  '
    if ((event.x >= self.box[0]) and (event.x <= self.box[2])):
        if ((event.y >= self.box[1]) and (event.y <= self.box[3])):
            self.movingCrop = True
            self.lastLocation = [event.x, event.y]