CS120 Assignment 6

CPSC 120 Fall 2007
Assignnment 6: Color Gradients
Due Friday, December 7, by 4 pm

Color Gradients

Color Gradients are a visual technique that blend two colors together; transitioning from one color to the another over a fixed space. The images below show some of the ways that Color Gradients can be used to achieve various visual effects. A) blends a bold color (blue) with the background color (white). The effect is that the bottom boundary of the box has faded away, while the top boundary is crisp and well defined. B) blends two colors to produce an effect that may resemble a sunrise. C) The word 'Hot' is reinforced by blending together colors reminiscent of fire. D) Blending colors that are slightly brighter and slightly darker than the background can produce a 3D effect.
Gradient Pictures

For this assignment, you will create a program that allows the user to select colors and blend them together to see their gradient.

Program Interface

Your program should display color menus at the top and bottom of the window. When the user clicks on a color in either menu a gradient between that color and the one in the other menu should be displayed in the space between the menus. When a different color is clicked on in either menu, the corresponding color in the gradient should change. Each menu should have at least five color buttons. Additionally, there should be a set of text boxes that allow the user to specify a "Custom Color" button. Remember that the Color class can specify colors in terms of Red, Green and Blue components (so you will need three text boxes as well as the corresponding button). A demo will be posted on the course web page to give you an idea of what the GUI should look like.

Program Design and Specifications

To complete this program, you will need to create three files: ColorButtonPanel.java, GradientPanel.java, and ColorGradientApp.java

ColorButtonPanel: This class is responsible for creating a menu of Buttons that allows the user to select the color to be used in the gradient.

It will consist of the following instance data:

At least 5 JButton objects to represent the colors(4 default + 1 custom)
At least 5 Color objects: Each button will have a color object associated with it.
A Color object to store the color of the button that was pushed last.
Three JTextFields to enter in the color components for the customized color and their corresponding labels.
2 ints to store the overall menu width and height in pixels.
A GradientPanel object - needed to tell what panel should be repainted when a new color when a button is pressed.

The following public methods are also needed:

A constructor -- takes the default starting colors and a GradientPanel and sets up the button panel (& the listeners needed)

setBackground

setPreferredSize

getSelectedColor -- returns a color object associated with the button that was last selected

The ColorButtonPanel class should have a nested listener class to listen for and respond to button clicks. When the Custom button is pushed the listener should get the red, green, and blue components from the text fields and create the current color.

GradientPanel: This class is the main panel where the gradients will be drawn

The following instance variables are needed.

Two ColorButtonPanels: one for the top, one for the bottom. Note that the constructors for ButtonPanels take a GradientPanel object. Since you are calling the constructor from inside of the GradientPanel class, you can use the keyword this to pass "this" object into ColorButtonPanel's constructor.
int width, height: the overall panel width and height in pixels
int panelHeight: a variable to track the height of the Gradient Panel that is eligible for drawing.

The GradientPanel class also needs to provide the following public methods:

A constructor -- sets up the components
paintComponent(Graphics page): The method should redraw the gradient to the screen. At a broad level, this is accomplished by starting at the top of the viewing region and repeatedly drawing horizontal lines across the screen until the viewing region is filled. Each time a line is drawn, the color changes slightly from the color at the top of the screen until it is completely transformed into the ending color at the bottom of the screen. Some good questions to think about:

How many lines will be drawn?
How much different is the top color from the bottom color? (Remember, colors are represented in terms of Red, Green and Blue components, so you probably want to ask How different in Red? How different in Green? and How different in Blue?).
If I know how different the first and last lines need to be and I know how many lines there are going to be, can I figure out how different each line is going to be? (in terms of Red, Green and Blue). Note: even though the difference in color (RGB values) are expressed in whole numbers, the difference from line to line may be fractional! Consider what happens if there are 100 lines to be drawn, but a color differential of 20.

ColorGradientApp: Contains the main method of the application - Creates a JFrame that contains a GradientPanel.

Implementation Strategy

As always, you should divide your work into small, manageable sections. Implement and test each section before moving on to the next. A suggested order is as follows:

Create the ColorGradientApp Class
Implement a GradientPanel class that is simply a colored panel.
Write the paintComponent method for Gradient panel that draws a gradient for two default colors (red and white).
Create a simple ColorButtonPanel that initializes 2 default colors.
Add a single ColorButtonPanel object to your Gradient Panal and verify that you can change between colors
Update the ColorButtonPanel to initialize 4+ default colors.
Add the second ColorButtonPanel object to your Gradient Panel; verify that you can change between colors.
Implement the Customize components on the ColorButtonPanel

Grading As usual your program will be graded on both style and correctness

Academic Integrity Reminder: Programming assignments are to be your own work. You may get help on the specifics of the assignment from no one except the instructor. You may not show your program to anyone or look at anyone's program or share ideas with anyone about how to write the program.

What to turn in