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)

What is wrong with this picture ?

Doing something useful with mirroring

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

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

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

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

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

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

Can we make a horizontal mirror?

Messing with Santa some more Copy bottom to top

Lab_1102 Complete the Python program for one of image processings (gray scale, sunset, posterizing) Write a Python program for a vertical mirroring Email the Python program file to comp1000.201@gmail.com