CS 100 - Computer Literacy, Spring 2005
This lab assignment will have you write a jython program
that will make a black and white version of a color image.
The program Jython Environment for Students (or JES) is the
development environment that we will use for this lab.
In the ACCC Labs that have JES, it can be found by:
- Clicking on Start
- Then click on All Programs
- Then click on Class Applications
- Then click on Engineering
- Finally click on Jython Environment for Students
Images Using a GrayScale
A black and white picture uses various shades of gray.
These shades of grey all have the same amount of red,
green and blue color. The higher the color value, the
lighter the shade of gray is. The lower the color
value, the darker the shade of gray is. For example,
look at the following squares for various shades of gray.
The amount of red, green and blue for the color is displayed
as text in each square. Note that the amount of red,
green and blue is the same in each square. Also note that
the larger the amount of color, the lighter the color of gray.
r = 0
g = 0
b = 0
r = 63
g = 63
b = 63
r = 127
g = 127
b = 127
r = 191
g = 191
b = 191
r = 255
g = 255
b = 255
Determining the amount of gray
One method to determine which grayscale color to use
for a pixel when creating a black and white picture
from a color picture is to average the amount of
red, green and blue color the corresponding pixel
in the colored picture. This method works fairly
well and is fairly easy to understand and use.
This way using the intensity of each color to determine
the grayscale value.
Another method is to take a weighted average of the
amount of red, green and blue color instead of an
evenly-weighted average. A weighted average would
give more weight to certain values and less weight to
other values. A weighted average will be used when
determining the grade for this course. Exams have a higher
weight (i.e. more impact on the final grade), while
lab assignments have a lower weight (i.e. less impact
on the final grade). For determining the amount of
color for the graycolor color, the original amount of
green is often given a higher weight while the original
amount of blue is given a lesser weight. The percent
of each color that should be used according to some
research done on luminanse is:
Lab Assignment 11
Due: Friday 4/7/2006 by 12:00 noon
Create a file using JES that will:
- Contain a comment indicating
- your Name,
- Course Name,
- Assignment Name and
- a short description of
- Contain a JES function that will
This function may call other functions that are built-in to JES or
that you have written.
- allow the user to pick an image using pickAFile().
- change the selected image to a black and white image.
To determine the grayscale color, we will use a third method.
This method uses a weighted average but puts less emphasis
on the color green that was done in the weighted average
discussed above. The percent to be used for each color is:
- display the black and white image.
- allow the user to save the image where the name of the
file is determined by using pickAFile().
On the ACCC lab computers, the H: drive is a permanent
storage area for you. Saving files to this drive on one
computer can be accessed from another computer (even another
computer in a different lab). It is suggested that you save
your python programs to the H: drive.
You are to submit the file containing the JES function
that you created to make the black and white image
by emailing it to the CS 100 course account at