- Location
- Trexler 363
- Times
- T/TH 10:10 - 11:40 AM
- Office Hours
- M-Th 6 - 7pm
- Office
- Trexler 365B
- chssmith AT roanoke DOT edu
Lab 10: Images
Greyscale
In a file called grey.py, write a function
called compute_greyscale(picture). This function should
alter the pixels stored inside of the picture object, so
that all three pixel values are averaged and set to that average. Your
function should then display the greyscale picture.
Example
Before
After
Hint
Use the makePicture function to create a picture in
JES. You can use the show function to display the
image to check to make sure it works.
The getPixels(a_picture) function returns a
collection of all of the pixels in an image. You can use this
function, as well as a for loop to examine and modify
each pixel in an image.
The getRed, getGreen,
and getBlue functions will give you the current
color of a pixel.
The setRed, setGreen,
and setBlue functions will let you set the color of
a pixel.
You can compute the average value by adding the red, green, and blue values, and dividing by 3.
Photo Negative
In a file called negative.py, write a function
called compute_negative(picture). This function should
alter the pixels stored inside of the picture object, so
that all three pixel values are their negated version. Your
function should then display the negative picture.
Example
Before
After
Hint
To make a picture the photo negative, you want to "invert" each of the red, green, and blue values. You can accomplish this by simply subtracting the current pixel's color value from 255.
You may wish to write 3 additional functions for this activity:
negate_red, negate_green,
and negate_blue. These functions simply negate
each of the color values for each pixel separately. Then you
just call these functions in your negate.