CS 170 Lab 11: Image Processing

This is a lab exercise that involves writing code that manipulates an image and displays it on the screen. Again I am strongly encouraging you to work on this lab in pairs.

I am strongly encouraging you to work on this assignment with another student. If you choose to work as a team, you must do the entire project together and you must contribute equally. When you submit your program, only submit it once (using either of your Truman usernames), but be sure to include both names in comments in the file.

Part 1: By the book (sort of)

For this part of the lab I want you to start with my version of the class negative code negative.py.

Try this code out on the image files lutherBell.gif and earth.gif. To try it out, type: 


makeNegative("earth.gif")
then try to find and display the graphics window that is created.

In this same file, type in the grayPixel function from class, which is: 


def grayPixel(oldpixel):
   intensitySum = oldpixel.getRed()+oldpixel.getGreen()+oldpixel.getBlue()
   aveRGB = intensitySum // 3

   newPixel = Pixel(aveRGB,aveRGB,aveRGB)
   return newPixel

As we did in class on Monday, rename makeNegative to changeImage and modify it to take a pixelChanger function as a parameter. Instead of calling the specific negativePixel function, your changeImage should call this parameterized value. Try calling changeImage with negativePixel and with grayPixel to make sure it works.

Part 2: Your Lab Assignment

For your lab assignment, you need to define a function called sepiaPixel to give the image that old-timey Western kind of look. Define this function in the same file as your functions from above.

The beginning of a formula for calculating sepia tones is: 


newRed = (R*0.393) + (G*0.769) + (B*0.189)
newGreen = (R*0.349) + (G*0.686) + (B*0.168)
newBlue = (R*0.272) + (G*0.534) + (B*0.131)
But note that there are two issues with these formulas. One is that the RGB values should be integers. The other is that sometimes these formulas will give values that are greater than 255. So, you need to come up with a sepiaPixel function that takes an input pixel and returns a sepia-toned pixel that has integer RGB values in the range 0-255. Try your sepiaPixel function by passing it as a parameter to your changeImage function. A particularly apt file for trying out sepia is OldCoots.gif.

This lab is due Thursday, November 15. When you are convinced that your code is correct, well-documented and your name is in the file, upload the file.