Spectrum 512 formats
The Spectrum 512 formats are a family of raster image file formats associated with the Spectrum 512 paint program for Atari ST.
There are three main file formats:
- Spectrum 512 Uncompressed (.spu)
- Spectrum 512 Compressed (.spc; signature="
- Spectrum 512 Smooshed (.sps; signature="
There is also said to be a backward-compatible "Enhanced" variant of the Uncompressed format, in which the palette colors have a slightly different format.
There is no easy way to distinguish Compressed and Smooshed formats, other than by the filename extension.
The image dimensions are always 320×199 pixels, though some decoders interpret them as being 320×200, with an all-black top row.
There are 4 bits of image data per pixel, which are interpreted using a complicated system of color palettes.
For uncompressed (.spu) files, the first 160 bytes are usually set to zero (except in the "Enhanced" variant). Following that are 31840 bytes of image data (160 for each row). Following that are 19104 bytes of palette data. The total file size is 51104 bytes.
Related formats described in other articles:
- http://samples.libav.org/image-samples/atarist/spectrum512/ - SPU, SPC
- http://cd.textfiles.com/geminiatari/FILES/GRAPHICS/SPECPICS/ - SPC, SPS
- http://cd.textfiles.com/806atari/301-400/315/ - SPS
- AtariForumWiki: ST_Picture_Formats (This page might be broken -- more info here.)
- MultimediaWiki article