1. CS 101 – Nov. 16 2 more major topics left: Image enhancement
Communication
Encryption
Networking
HTML

2. Enhancing an image Input = original image (x) Output = final image (y)

3. Brighten To brighten, we increase pixel values.
Simple function like y = x + 20 won’t work
Real filter functions have complex formulas
Better to “draw” the filter function

4. Filter function
Axes for input and output pixel values
255
255
255
255

5. Brighten
We want output > input.
255
255
brighter
darker
255
255

6. Darken
We want output < input.
255
255
brighter
darker
255
255

7. Increase contrast
What do we want?
255
255
brighter
darker
255
255

8. Increase contrast Bright get brighter; dark get darker 255 255
255
128
255

9. Decrease contrast? What should this look like? 255 255 brighter darker
255
128
255

10. Decrease contrast
“Robin Hood”
255
255
brighter
darker
255
128
255