CS 101 - Introduction to Computing, Spring 2007

Lab 7

This lab assignment will have you write a function in jython that will either lighten or darken an image by an amount given as a parameter.

Reminder

In the ACCC Labs that have JES, it can be found by:

1. Clicking on Start
2. Then click on All Programs
3. Then click on Class Applications
4. Then click on Engineering
5. Finally click on Jython Environment for Students

Use of makeDarker() and makeLigher()

• makeDarker() will decrease the values for all three color values (red, green and blue).
• makeLighter() will increase the values for all three color values (red, green and blue).

As it turns out makeDarker() decreases values for each color by 30%, while makeLighter() increases the values for each color by about 40%.

Lab Assignment 7

Create a file using JES that will:

1. Contain a comment indicating
   • your Name,
   • Net-ID,
   • Course Name,
   • Assignment Name and
   • a short description of the assignment

2. Contain a JES function called modifyBrightness() that will
   • take a percent value as a parameter given as an integer number.
   • allow the user to pick an image using pickAFile().
   • darker or brighten the image by using either makeDarker() or makeLighter()
   • display to modified image
   • allow the user to save the modified image in a file whose name is specified by using pickAFile().

   If the parameter is a positive number, use makeLighter() to brighten the image. If the parameter is a negative number, use makeDarker() to darken the image. You may also need to call makeLighter() or makeDarker() multiple times based on the actual value of the parameter.

   For example, let us assume that modifyBrightness() is called with a parameter of -90. The call in the command area of JES would be:

   >>> modifyBrightness (-90)

   This command is telling us to darken the image by 90%. Since makeDarker() darkens a color by 30%, we will call makeDarker() three times to achieve this effect, since 90/30 equals 3. (Note that this calculation and logic is slightly flawed, but we will ignore that for this lab assignment.)

   For example, let us assume that modifyBrightness() is called with a parameter of 80. The call in the command area of JES would be:

   >>> modifyBrightness (80)

   This command is telling us to lighten the image by 80%. Since makeLighter() lightens a color by about 40%, we will call makeLighter() twice to achieve this effect, since 80/40 equals 2. (Again note that this calculation and logic is slightly flawed, but we will ignore that for this lab assignment.)

   If we are darkening the image, divide the parameter value by 30 and call makeDarker () that number of times for each pixel. If we are lightening the image, divide the parameter value by 40 call makeLighter() that number of time for each pixel. You are to preform integer division, thus ignore any results after the decimal place. For example

   • 20/30 => 0
   • 40/30 => 1
   • 60/30 => 2
   • 80/30 => 2
   • 100/30 => 3
   • 120/30 => 4

   Therefore:

   • if a parameter value is that is between zero to 39, makeLighter() will not be called.
   • if a parameter value is that is between 40 to 79, makeLighter() will be called once.
   • if a parameter value is that is between 80 to 119, makeLighter() will be called twice.
   • if a parameter value is that is between -1 to -29, makeDarker() will not be called.
   • if a parameter value is that is between -30 to -59, makeDarker() will be called once.
   • if a parameter value is that is between -60 to -89, makeDarker() will be called twice.

   This function may call other functions that are built-in to JES or that you have written.

Submittal of the Lab Assignment

• You are submit your program electronically by placing it in the digital drop box in blackboard.
• Programs that are correct and submitted by noon on the Wednesday the lab assignment is discussed will receive an extra 10% on the score of the lab.
• When saving your program, use a meaningful name like lab7.py.
• When submitting your lab assignment, place all of the needed files it in a zippped folder (even if you are only submitting one file) with the name of yournetid_labX and submit that zipped folder to the digital drop box. For instance, if your net id is abc32 then the folder name should be abc32_lab7.

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