Assignment A6: Paint Program

Overview. In this assignment, you will write parts of a simple paint program. Some of
the functionality you will implement is:
1. Freehand drawing and erasing,
2. Airbrushing.
3. Drawing lines.
You can work in groups of two. Form the group well before the assignment due date.
Both must do something to form the group: one proposes, the other accepts. People in
a group must work together. It is against the rules for one person to do programming on
this assignment without the other person sitting nearby and helping. Take turns ”driving”
—using the keyboard and mouse.
With the exception of your CMS-registered group partner, you may not look at anyone
else’s code, in any form, or show your code to anyone else (except the course staff), in any
form. You may not show or give your code to another student in the class. You may not
look at solutions to similar problems in previous semesters.
1 Installing the code
The release contains a directory src that countains .java files and directory images that
contains .png files (these are images). Follow these steps to install the code in an Eclipse
project:
1. Create an empty Java project.
2. Copy the two directories into the root directory of the new project. (Click overwrite
when it asks if you want to overwrite director /src.)
You package explorer should now look like this:
Method main for the program is in file Window.java.
CS 2110 Spring 2018 1/7 Assignment 6
2 Paint program
You can see a screenshot of a fully implemented paint program in Figure 1, where we also
show it annotated with what the important GUI components represent.
• The program allows you to open image files and save in images files. See Figure 2.
• You can draw with a pencil (freehand drawing), erase, airbrush. You can draw lines
and circles. You can change both the foreground color (used for drawing) and the
background color (used for erasing). See Figure 3.
SAVE: The program lets you know when there are unsaved changes to the image.
Label “SAVE” appears at the bottom whenever changes are made and disappears
when the image is saved to a file.
You will see some more functionality by running the release code.
3 Project Structure
A significant part of your work for this assignment will be to read the release code and figure
out how it works. You may need to find the relevant Java documentation on the Web and
read it. Successful completion of the assignment requires you to understand well how the
existing code works. Here is a brief description of classes:
Window: This class sets up the main window of the program. It handles the creation of most
GUI components and responds to relevant actions.
Canvas: This class represents the image you are painting. It handles the mouse events that
are relevant for drawing and performs the drawing operations.
NewImageDialog: A custom dialog for creating new blank images.
Tool: An enumeration of the available drawing tools.
Window and Canvas are the only classes you need to modify. Do not change anything
else in the code. Every point inside the code where you have to change/add something
has been marked for you with a //TODO comment.
4 Class Window
Class Window contains the first five TODOs; the parts that have to be implemented have
been clearly marked in the release code. You will need to:
1. Implement the toolslider. When dragged up and down, it should change the sizes of the
tools used on the canvas, and the current tool size should be displayed in the bottom
of the window as shown in Figure 1.
CS 2110 Spring 2018 2/7 Assignment 6
2. Implement the image size label. It should display the size of the image currently on
the canvas, as shown in Figure 1.
3. Implement method getIcon, so the foreground and background buttons display a color
(as shown in Figure 1) instead of the default text.
4. Fix the forground color so that it updates when you select a new color.
5. Fix the background color so that it updates when you select a new color.
These methods are relatively simple (a few lines of code), but you need to read and
understand the code well before you attempt to make any changes.
5 Class Canvas
Class Canvas contains TODOS 6-10; the parts that have to be implemented have been clearly
marked in the release code with a //TODO comments. You will find detailed instructions
in the code. You will need to:
6. Modify the mouseMoved event handle to display the current mouse position in the
window (as show in Figure 1).
7. Implement the pencil/eraser helper method colorClick, which draws when the pencil
or eraser is used.
8. Implement the pencil/eraser helper method colorDrag, which draws when the pencil or
eraser is used. Note: freehand pencil drawing should leave no gaps. That is, when you
press and drag the mouse around, it should draw on the trace of the mouse movement.
9. Implement the airbrush. The airbrush does not have to leave a continuous trace.
10. Implement the line (note that there are three parts to this: 10a, 10b, 10c). We suggest
you implement line drawing as follows: When you first press the mouse, one endpoint
of the line is fixed (nothing is drawn on the image yet). When you press the mouse for
a second time, the second endpoint is fixed and the line is drawn on the image.
You should visualize the “tentative line” after the first endpoint is given and before the
second endpoint is given. That is, while the user is deciding on the second endpoint
and moving the mouse around, they can see the line that will be drawn.
Pinned piazza note A6 FAQs contains a schedule of tasks to be done, with a separate note
in each giving an explanation. With each task, we also give a suggested time to complete it.
6 Submission
Compress exactly the following files into a zip file that you will then submit on the CMS:
CS 2110 Spring 2018 3/7 Assignment 6
• README.txt: This file should contain your name, your NetID, all known issues you have
with your submitted code, and the names of anyone you have discussed the homework
with (except the course staff). Also, if you want to explain something about your code
that you think needs clarification, add a few paragraphs here.
• All the .java files needed for your program.
Do not include any files ending in .class.
All .java files should compile and conform to the prototypes we gave you. We write our
own classes that use your classes’ public methods to test your code. Even if you do not use
a method we require, you should still implement it for our use. Do not change the signature
of any method that is in the release code.
6.1 Grading,
Solutions will be graded on correctness, the quality of the algorithms, and style. A correct
program compiles without errors or warnings and behaves according to the requirements
given here and in the comments of the code. A program with good style is clear, concise,
and easy to read.
CS 2110 Spring 2018 4/7 Assignment 6
Figure 1: Fully implemented paint program.
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Figure 2: Open and save image files.
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Figure 3: Drawing.
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