DL

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NAME

dl - format of DL animation files

DESCRIPTION

DL files (with suffix .dl) contain bitmapped images, a color map, and a set of commands to animate the images. DL files are not that predominant (I have only a very few). There is little official documentation that I have found. This file is merely an attempt to document the file format.

There are (at least) 2 versions of DL files: version 1 and 2.

DL version 1 file format is:

 Size
(bytes)         Description
-----------------------------------------------------------
1               Version number (1). Image format (implicit)
                is 1 (medium)
20              Title (XOR'ed with 0xff).
1               Number of screens (nscr).
1               Number of commands (ncmd).
1               Unknown. Something to do with colormap and
                border colors.
768             Colormap (3 bytes per color, 256 colors)
320*200*nscr    Data for each screen (always 64000 bytes).
ncmd            Commands in an unknown format. The last
                command can be negative (unknown reason) and
                is to be ignored.

DL version 2 file format is:

 Size
(bytes)         Description
-----------------------------------------------------------
1               Version number (2).
1               Format (0=large320x200, 1=medium160x100).
20              Title (XOR'ed with 0xff).
20              Author (XOR'ed with 0xff).
1               Number of screens (nscr).
1               Number of commands (ncmd).
3               Unknown. Something to do with colormap and
                border colors.
768             Colormap (3 bytes per color, 256 colors).
320*200*nscr    Data for each screen (if format==0, single
                image per screen, if format==1, 4 images
                per screen)
2*ncmd          Commands, little-endian (byte swapped 16-bit
                words). The last command can be negative
                (unknown reason) and is to be ignored.

Commands appear to be just a list of frames to display in a loop. For example, given four frame images (0 through 3), the commands:

: 0 1 2 3 2 3 2 3 2 1 2 1 2 1

can create an animation showing these frames in succession. You can thus have far fewer actual bitmap images that "frames" in the animation loop.

AUTHOR

Bill Rosenkranz <rosenkra@convex.com> based on xdl program by Jonas Yngvesson <jonas-y@isy.liu.se> for the X Windows xdl.

This document was created by man2html, using the manual pages.
Time: 02:28:52 GMT, February 15, 2023