<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def scale_cb(self, setting, value):
 """Handle callback related to image scaling."""

        zoomlevel = self.zoom.calc_level(value)
        self.t_.set(zoomlevel=zoomlevel)

        self.redraw(whence=0)