[Freeciv-Dev] unit animation file format

[Lukas Tönne <lukas.toenne@xxxxxx>]

I've got an important question (should i say problem ?) for the freeciv 
developers now:

What file format would be the best for the unit animations i'm working on ? 

I think the easiest way to _implement_ such animated graphics would be one big 
(png-) file with all the single images appended to each other in a line or 
grid (as for example in the old "unit explosion" or the iso_nuke.png that is 
already used in the SDL client). Anyway, this might not be the best solution, 
because the resulting file would be extremely large in terms of width and 
height (at least 1280x3200 using the specification i described below) as well 
as in terms of file size (about 1MB per unit, 250KB when using indexed 
colors). I don't know if the supported png filesize is restricted in any way, 
but downloading would also get a big problem since we have about 50 unit 
types by now (the filesize already refers to compressed files).

A possible solution could be using the FLI/FLC file format or something 
similar. AFAIK this format is used by many computer games for (unit- ?) 
animation, etc. and might offer a better compression for such files. What i 
don't know is if this file format is open source and if not if there are any 
free formats with the required functionality (gotta check that out). Does 
anybody have any experience with that ? 

The second point to discuss is the geometry of the actual animation images. i 
suppose a singe image format of 80x80 pixels with the upper corner of the 
units ground square in the middle and "tolerance" borders of 8 pixels, which 
would prevent details from "slipping" out of the frame and allow nicer 
animations. Have a look at the attached file, this should make it clear.
I think it's enough to have 16 images per animation and every animation 
rendered in 8 directions.

unit_format2.png
Description: PNG image