1. Gray Scale picture def pixBW(pixel): # given a pixel, change to BW
get R,G,B values of the pixel
compute the average
set R,G,B values of the pixel to the average
return
def picBW(pic):
get the width of pic, and name it
get the height of pic, and name it
for every y coordinate:
for every pixel in the row at the given row y:
call pixBW(pixxx)

2. What is wrong with this picture ?

3. Doing something useful with mirroring

4. Vertical Mirroring
Imagine a mirror horizontally across the picture, or vertically
What would we see?
How do generate that digitally?
We simply copy the colors of pixels from one place to another

5. Vertical Mirroring 1 2 3 4
Think of a number at each x and y location instead of a color
Note that the distances from the middle column are identical in both directions 1 2 3 4 5 1 2 1 2 3 5 4

6. How do we design Algorithm for this ?
Slicing a picture down the middle and sticking a mirror on the slice
Do it by using a loop to measure a difference x
mirrorpoint y x x

7. Algorithm (recipe) Use a distance from the mirror point
Then reference to either side of the mirrorpoint using the difference

8. 1 2 3 4 5
Loop through all the rows (y starts at 1, increments by 1, and is less than the picture height)
For each row,
Loop with x starting at 1 and x less than the midpoint (mirror point) value
Get the left pixel at (mirrorpoint-x, y)
Get the right pixel at (mirrorpoint+x, y)
Set the color for the right pixel to be the color of the left pixel 1 2 3 5 4

9. How does it work? Compute the half-way horizontal index
The y value travels the height of the picture
The x value is an offset
It’s not actually an index
It’s the amount to add or subtract
We copy the color at
mirrorpoint-offset to mirrorpoint+offset

10. Can we make a horizontal mirror?

11. Messing with Santa some more
Copy bottom to top

12. Lab_1102
Complete the Python program for one of image processings (gray scale, sunset, posterizing)
Write a Python program for a vertical mirroring
the Python program file to