def decrease_brightness_GUI (label):
'''Implement the decrease_brightness function from img_manip.'''
#Clear all the temp pics in front of the current pic current_pic
global temp_label
global current_pic
temp_label = temp_label[0:current_pic+1]
#Implement the function decrease_brightness
label.picture = img_manip.decrease_brightness(label.picture)
#Keep a copy of the current pic for the functions Undo and Redo
temp_label.append(label.picture)
current_pic += 1
#update the label
update_label(label)
def test_decrease_brightness():
'''Test the function decrase_brightness in img_manip.'''
new_pic = create_pic(4, 4)
new_pic_decrease_bright = img_manip.decrease_brightness(new_pic)
#The average brightness of new_pic_increased_brightness will likely not be
#exactly 10 less than that of new_pic because some RGB values may already be
#0 and cannot decrease, so the function tests for a difference of 10 with
#an error of 2 rather than for strict difference of 10.
old_avg_brightness = avg_bright.average_brightness(new_pic)
new_avg_brightness = avg_bright.average_brightness(new_pic_decrease_bright)
assert old_avg_brightness - new_avg_brightness- 10 < 2, \
"decrease_brightness failed to decrease the picture's average \
