WhirlGIF Version 2.0
Documentation

WhirlGIF is a quick program that reads a series of GIF files, and produces a single gif file composed of those images.

Usage:
	whirlgif [-v] [-trans index ] [-time delay] [-o outfile] [-loop]
		 [-disp none|back|prev|not]
		 [-loop] [-i incfile] file1 [ -time delay] file2

options

-v

Verbose mode

-loop [count]

Add the netscape 'loop' extension, with an optional [count] number.
If given, 'count' will set the number of times to repeat the sequence. Current Netscape versions ignore the count and always repeat infinite times.

-disp

Set disposal method
This determines how the program displaying the image should treat the image after being displayed. There are currently four possible options:

• none No disposal specified. The default.
• not Do not dispose. The next image will overlay this one.
• back Restore to background color.
  Fill the image's space with the previous background color. May cause flicker.
• prev Restore to previous.
  Restores the previous frame's data.

-trans

Set image transparency.
This can either be a number 0-255 signifying the colormap index to set transparent, or a RGB color specification in the format #RRGGBB to set the first color matching the given value to be the transparent color. Note that in some user shells and most scripts, the string with the # (pound) sign must be quoted. For example:

          whirlgif -loop 5 -trans "#00f10e" tv*.gif

-time delay

Set the delay time between frames to 'delay', which is a value from 0 to 65536 giving the time to sleep in 1/100s of a second.

Some example times and approximate frame rates

• 5 = 20 frames per second
• 10 - 10 frames per second
• 20 - 5 fps
• 100 - 1 frame per second

-o outfile

Write the output to 'outfile' instead of standard out.
By default, the program writes the GIF sequence to stdout, which is a good thing if you're using this in a CGI script, a very bad thing if you run this from a terminal and forget to redirect stdout.

-i incfile

Read the list of files to process from 'incfile'.
This can be very useful for systems with short command line buffers, and for scripted generation of long animations.

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Hints and Tips

The output file (if any) and -loop _MUST_ be specified before any gif images.

You can specify several delay statements on the command line to change the delay between images in the middle of an animation, e.g.

       whirlgif -time 5 a.gif b.gif c.gif -time 100 d.gif -time 5 e.gif f.gif

Although it's generally considered to be evil, you can also specify several transparency statements on the command line, to change the transparent color in the middle of an animation. This may cause problems for some programs.

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Known Bugs

• The loop 'count' is ineffective because Netspcape always loops infinitely.
• should be able to specify delay in an 'incfile' list (see next bug).
• Does not handle filenames starting with a - (hypen), except in 'incfile'.
• Needs better documentation.

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Future Features (TODO List)

Only save colormaps that are different from preceeding ones.

This will saves space, CPU time, and reduce compatibility problems

Save only the changed part of images

Add an option to compare each subsequent frame after the first, then only save the smallest rectangle the encompasses changed areas of the image. Using this option can make for VERY small animations, however, it is likely to be incompatible with most badly-written rendering code, and the best algorithms for this process are patented.

option for luma sorting of colormaps

This speeds up rendering and helps on displays with limited color capabilities (e.g. most MS-Windows and many X-Windows systems).

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If you're reading this as a text file or from some other site, This program is available from http://www.msg.net/utility/whirlgif/. The program is based on the 1.10 release of 'txtmerge' , written by Mark Podlipec podlipec@wellfleet.com