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Working with Images

Unfortunately, different kinds of applications typically require images in different file formats. Moreover, the image file you have is almost never the right size or resolution or format as the image file you need. The process of converting from one to the other occasionally leads into a hopeless morass. However, by knowing a few basic tools, you can usually get by.

In general, you will want to do your image processing on SGI machines. This page assumes you are working on an SGI machine.

Viewing your files

PostScript -- to look at PostScript files, use the command ghostview filename.
Binary Files -- to look at most other formats, like .gif, .sgi, .tiff, .pnm, etc, you have two good options:
imgsee filename
display filename
There are subtle differences, but generally it doesn't matter much. If you are having trouble with one, try the other.

Converting Files

A good place to start is with the convert program. Its syntax is
convert filename.ext1 filename.ext2
If that doesn't work, you should try the pbm toolkit utilities. These converters convert a huge range of formats from and to .pbm, .pgm, .ppm and .pnm formats. Thus by doing two conversions, you can in theory get from anywhere to anywhere. Note that .pbm is black and white, .pgm is grayscale, .ppm is color, and .pnm will use its judgement. In general, use the .pnm utility. For a partial list of the pbm toolkit converters, check the man page.
For PostScript, try the ps2raw utility. It's syntax is
ps2raw filename.ps > filename.raw
Once you have a .raw file, you can try processing it with convert.

Changine Size and Other Image Processing

In general this is fairly technical. If you don't mind wading through man pages, start with the image utilities page in the software overview. Otherwise, you will probably want to consult with the Center staff.

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Created: Fri Sep 8 11:39:00 1995 --- Last modified: Jun 18 1996