Customization the External Commands:

You can customize these commands by editing the StageTools/lib/commands.tcl file; all the modules look here to find out what commands to use for these functions. The routines in this file each return a string that is the command to perform for that function. For example, the command _viewer(Image) should accept an optional file name and return a string that contains the command to perform in order to view the file. The other procedures in the file work the same way. Several of these commands look up X resources to find the command to use, so this provides an easy way for users to customize the commands they want to use. The defaults are set in the option commands at the top of the commands.tcl file.

You may want to edit either the option commands or the procedure definitions themselves. For example, the ImageMagick package no longer produces compressed GIF files (in an attempt to avoid patent troubles), so the GIF files it produces are much larger than they need to be; you may want to substitute some other command for producing GIF files. Here is one possible solution:

    proc _cmd(Convert) {old new type w h colors dither} {
      global _image
      set options "-geometry ${w}x${h} +comment"
      if {$colors != ""} {
	if {$dither} {append options " -dither"} \
                else {append options " +dither"}
	append options " -colors $colors"
      }
      switch $type {
        jpg {append options " -quality $_image(quality)"}
        gif {return "convert $options $old PNM:- | pnm2gif > $new"}
      }
      return "convert $options $old $type:$new"
    }

The _cmd(Convert) procedure is used in two distinct ways: 1) to convert ppm files to other formats, and 2) to resize an existing image. If you do not have a program like convert that can read any input format and produce any output format, you may need to have a more complicated switch statement that takes into account both the input and the output formats. Usually you can tell the format from the file extension, but this is not always the case. You can make the following assumptions: the "type" variable always gives the type of the output file, and if the old name is not the same as the new name, then the file extension of the old name gives its type (if you don't recognize the type, assume it is PPM).

If you modify _cmd(Convert) to work with packages other than ImageMagick, please consider sending us a copy of your code so that we can share it with others who may also want to use the same package. Send your modifications to software@geom.umn.edu.

[More examples are needed here]

If you plan to change the MPEG encoder, you will also need to edit the StageTools/module/BackStage/mpeg.tcl file, as this file includes the procedures that write the .param file that is passed to mpeg_encode. Since this command file is specific to mpeg_encode, if you want to substitute some other MPEG encoder, you will most likely need to modify the .param file format. There are procedures in mpeg.tcl that are called to write the data at the beginning of the file, the data at the end of the file, and the data for individual frames of the file. If you modify mpeg.tcl to work with some other MPEG encoder, please consider sending us a copy of your code so that we can share it with others who may also want to use the same encoder. Send your modifications to software@geom.umn.edu.

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Created: Aug 20 1997 --- Last modified: Thu Aug 13 08:20:32 1998