Format conversion and animation

File conversion with ImageMagick

ImageMagick is a free open-source program package that can perform a variety of image manipulation tasks. The program 'convert' can convert files to and from virtually any graphics format. The following command converts a PostScript file to the gif format; 
 convert file.ps file.gif
The image can also be processed in different ways. For example, to remove extra white space from around a figure, leaving only a rectangle enclosing the actual graph, use the -trim option: 
 convert -trim file.ps file.gif
For a full list of options, consult the ImageMagick web-site or the 'man' pages (man convert or man ImageMagick).

Animation with ImageMagick

Animations can be produced very easily by ImageMagick. The command 
 convert -delay 20 files*.ps animation.gif
converts all files files*.ps in the current directory into the gif format, merging all of them together in a single file animation.gif. The -delay 20 option indicates a time-delay o 20/100 s between the images when the file is viewed (using, e.g., a web-browser, Quicktime, RealPlayer, or in a presentation program such as Powerpoint or Keynote).

If one wishes to remove extra white space from the ps images, the -trim option can be used. In order to have exactly the same clipping in each of the images, one can add a box enclosing the desired area in the postscript files (if some corresponding bounding feature is otherwise not present). One can also first convert the ps files to encapsulated PostScript, but these files tend to become very large and the process is slow (on sone displays this conversion also leads to color problems when viewing the gif animation).

This way of creating animations work well if the number of images and their sizes are not too large (at least up to around 100 ps images of size tens of kilobytes each).

In order to make animations this way, a series of consecutively numbered ps files have to be created. An example of a Fortran 90 program doing that is discussed here (along with an animation created with convert as discussed above).