Example code - COM1370 Computer Graphics - Summer 2003

Professor Futrelle, Northeastern University, CCIS

This page includes pointers to source code, to directories containing sources and executables and to sites that have sample graphics code. In particular, here is a link to a number of directories and files.

If you want to ftp to the directory where the files are in order to transfer them that way, you'll want to move to this directory: /home/futrelle/.www/teaching/com1370sm2003/examps/examps/

You are welcome to adapt any of the code you find here for your projects. You may also want to adapt code you find elsewhere. But it's very important that you write most of the code yourself. It's also important that you carefully describe the origin of any code that you adapt. I'm quick to notice code that is not code you wrote yourself, believe me. Using others' code and pretending it's yours is plagiarism and a violation of the university's code of conduct.

A Sun site has many Java 2D examples.

Notes on selected examples

When all the examples from the Sun site I've included are added up, there are too many to comment on individually. But below are comments on selected ones of mine and a few from the Sun site. See also my comments on timers, which can be useful for animation.

• TinyDraw is about as simple a Swing application as there is. It creates a window, draws a bit of text and then creates and fills a three-sided path, a triangle. Here's the directory that has the single source file and the compiled file.


• Here's a bit of code that creates and prints out some 2D transform matrices (3x3). It doesn't do any transforms -- I leave that up to you! That is, you'll need to write a few loops that multiply a matrix times a vector and multiply two matrices together. These are best defined as static methods in a single matrix class your create, just as are functions in the java.lang.Math class, e.g., the Math.sin() and Math.cos() methods. Hint: For each [i][j] in your matrix multiplication loop, you'll want to initialize the resulting product element to 0.0 and then add (+=) the products of the appropriate elements of the two matrices. Just remember your linear algebra: M_ij = Σ_k M_ik*M_kj.


• Controlling graphics with menus is shown in the simple application ShowRectOval, which can be found here. This demo uses simple AWT graphics drawing, not Java2D. But the emphasis is on the menu control, not the graphics.


• This simple scrolling example scrolls only text, but it does show the use of JScrollPane. The strategy, as shown in Scroller.java, was to create a TextPanel, size it, create a JScrollPane holding the TextPanel and then add the JScrollPane to the ContentPane of a JFrame. Of course it's possible to put any of a variety of Containers in a JScrollPane and they just work.


• SimplestDraw draws a triangle filled with red and bordered with green. It also draws a rectangle and a translated rectangle (not translated by a translation matrix, but more simply).


• SwingApplication is another extremely simple Swing example that has one class for the GUI and another for the component that is drawn, a single line. It uses simple graphics, not Java 2D.


• DragKing is a nice little application that I found on the Web. It demonstrates the use of the mouse to move objects around. In addition, it demonstrates Java2D's ability to draw quadratic and cubic curves (Bézier curves), curves we will discuss in this course and which are described in our textbook. The mouse hit is checked to see if the mouse click is within a small square region, using Java's contains() method. The contains() method is defined for the java.awt.Shape interface and specifically for the java.awt.geom.Rectangle2D.Double class which implements Shape and is used in this demo.


• Local copies of a large number of Java2D code examples can be found here. This page gives you access to the source and to applets you can run, but only if you have something more than Java 1.1 as a browser plugin. (7/03: MS will be dropping Java from its platform but Dell and HP will now include full Java in all their systems starting in 2004, as I understand it.) More simply, you can just compile and run the source of any of the demos yourself. A zip file of the demos is in the directory linked above. You can run all the apps, one after the other, by executing the .sh or .bat file included. You may well find a demo here that will help you with your course project.


• Winding is a small demo that illustrates how complex shapes are filled. For example, the shape of the letter O is composed of an outer and an inner contour and only the region inbetween should be filled. This is what the "winding rule" handles. In doing this sort of thing you have to realize that the two contours can be drawn with the same sense, both clockwise or counterclockwise, or with opposite senses.

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