So far we've asked for a brightness and received a rectangle of that brightness. Now let's think about what would happen if we changed the brightness of an image. Start with the image on the right.

First we decrease its brightness. Notice how the image gets darker and darker.

Then we increase its brightness, and the image gets brighter and brighter.

-20

-40

-60

+20

+40

+60

Now you try changing the brightness of an image.