Command-line usage

Most of these switches behave more-or-less the same on the Windows, Linux, and RiscOS versions; some RiscOS-specific issues are mentioned below. Note that even on the Windows version, the options must be prefixed with - and not /.

At its simplest, you can just type intergif and the name of your sprite or film file, and it'll be converted. Here's a full list of the options:<>

intergif [-i] [-s] [-loop] [-split] [-d cs] [-t [pixel]] [-trim] [-join] [-list] [-g16 | -g256 | -216 | -256 | -pal palfile | -best n ] [-dither [-zigzag]] [-c changefsi-options] [-o outfile] infile

-i: Produce an interlaced GIF: in other words, one which a Web browser can render quickly at a low resolution, filling in the details later as they arrive.
-loop: Looping animation: Normally an animated GIF plays through once and stops. If you tick this option, you'll get an animated GIF that plays over and over again.
-join: This option causes InterGif to look for only one frame in the file you give it, and then look for the next frame in another file with the numeric part of the file incremented. For instance, you could have three files called frame000, frame001, and frame002 and create an three-frame animation by issuing the command
intergif -join frame000 -o frames/gif
This is, by no coincidence, compatible with the way POV-Ray names its output files.
-list: This option causes InterGif to treat "infile" as a text file containing a list of image filenames to convert.
-d cs: Sets the frame delay in centiseconds. This overrides any frame delays set in the input file or files.
-split: This splits up the input file into one output file per frame. Not, I admit, terribly useful, unless you need to import something into an application that expects lots of one-frame GIFs -- for instance, Sun's Java Animator applet. The names of the files are taken from the one you give, with any numeric part incremented as needed, so if you save a three-frame animation as frame001/gif, you also get frame002/gif and frame003/gif.
-t: Use transparency (masking) information from the input file to determine transparency in the output file (the default is to use no transparency at all).
-t pixel: Use the specified pixel-value from the input file as transparent.
-trim: This tells InterGif to remove any wholly transparent rows or columns from the edges of the input image. (If the input is an animation, it only removes rows or columns that are blank on every frame.) This means that the output image may be a different size from the input one, which is otherwise never the case.
I'd advise you to do this if you're making a one-frame, transparent, interlaced GIF: for the reason why, see the section on Netscape Navigator 4.
You probably also want to do this if you're converting a Draw file, as these often end up with one or two transparent rows and columns at the edges.
-216: This maps all colours in the input onto the nearest ones in the Macintosh/PC standard 216-entry "web safe" colour cube. This is useful, for instance, for reducing the size of 256-greyscale images. Note that InterGif really does map the image to the new palette: it doesn't do dithering, unless you also use -dither. Properly dithered images compress really badly in the GIF format.
-g16
-g256: These options cause InterGif to create greyscale output: 16 or 256 greys respectively.
-best n: This is the most powerful option: selecting this makes InterGif calculate the optimal palette for displaying the input images, and then map to that. You can tell it to calculate any size palette from 2 to 256 entries. InterGif uses the "median cut" algorithm to calculate the palette.
-dither: Selecting this option makes InterGif dither, rather than map, its input file to the required palette. This only works on 16bpp and 24bpp input files (and Draw files). This feature was contributed by Martin Würthner.
-zigzag: Normally the -dither option works left-to-right on every row. But you probably want it to alternate left-to-right and right-to-left on alternate rows -- this so-called "boustrophedonic" Floyd-Steinberg often gives better results, and it's what ChangeFSI uses. The -zigzag option makes the dithering boustrophedonic.
-o outfile: Filename for the output (default is <infile>.gif)
infile: A RiscOS sprite, Draw, Complete Animator, or GIF file (the first two of those only work on the RiscOS version)

RiscOS version only

As well as allowing the conversion of sprite files and Draw files, the RiscOS version of InterGif supports the following extra options:

-s: Produce a sprite rather than a GIF
-256: Map to Acorn standard 256-colour ("mode 15" or "VIDC1") palette
-new: Output a "new format" (RiscOS 3.5 and later only) sprite
-xdpi 180 | 90 | 45 | 22: Horizontal dpi specification (for new format sprite only)
-ydpi 180 | 90 | 45 | 22: Vertical dpi specification (for new format sprite only)
-pal palfile: Map to given palette
-c changefsi-options: Preprocess each frame with Acorn ChangeFSI, if available

The default output file is <infile>/gif instead of <infile>.gif.

(Note to users of previous RiscOS versions: the !Boot file of !InterGif sets up Alias$intergif, so you no longer need to copy the intergif program into your library directory. In fact, to avoid confusion, you should go and delete any copy of intergif in your library directory.)

All Rites Reversed -- Copy What You Like