This file save filter writes a large regular grid filled with coloured characters. The characters can be stored in file and don't have anything to do with the image. The colour of each character, though, is taken from the image to save.
This creates some kind of mosaic effect with characters.
The pictures should be limited to about 120x120 pixels, since most browsers do not view larger images. The aspect ratio depends on the fixed-width font the browser is using, and is usually around 2:1 (so you should squash your image accordingly).
The FONT tags can be saved either HTML-4.0 compliant (
font color="#rrggbb") or in a proprietary format most browsers support (
font color=rrggbb). To save even more space you can leave out the closing tag (
/font), but this will potentially leave thousands of font elements open in the browser, and will disturb the current font colour.