Creating an Animated GIF Image

by D.W. Hyatt

Creating an Animation

Various graphic images can be animated using a module from the UNIX program called ImageMagick. The graphics can be either grabbed with xv from a running program or generated by some other means. To simplify the animation process, the files should be named in some logical sequence so that the order they are listed in the directory is the order in which they are to be animated. ImageMagick can handle a number of different file formats, but in this case we will use .gif because eventually we will make an animated GIF image for use on a web page.

To just animate the various frames, just type:

animate sphere*.gif

sphere00.gif	sphere01.gif	sphere02.gif	sphere03.gif
sphere04.gif	sphere05.gif	sphere06.gif	sphere07.gif
sphere08.gif	sphere09.gif	sphere10.gif	sphere12.gif

This will take the files that start with sphere and end with .gif and will animate them in sequence depending upon their file names. That is why it is convenient to have them named with a numerical value attached. With ImageMagick, there are controls to speed up or slow down the animation as well as make it go forward or reverse.

Making an Animated GIF Image

To create an animated GIF image, ImageMagick has another routine that is quite helpful called convert. Although it is possible to convert directly from the PPM images, it is better to use xv to make some smaller GIF images of each frame, and then use the command:

convert -delay 20 -loop 0 sphere*.gif animatespheres.gif

This will take all of the source frames and will make them into one animated GIF image called animatespheres.gif. The -delay 20 argument will cause a 20 hundredths of a second delay between each frame, and the -loop 0 will cause the gif to loop over and over again.

Click on the image to the right to see it animate.