BSI texture file format
Standalone image chunks used by named textures such as sky and sun images.
Overall structure
Unlike a TEXBSI archive, a standalone BSI has no 9-byte image name or record-size envelope. It begins directly with tagged chunks:
[IFHD or BSIF — image marker]
[BHDR — image header]
[CMAP — optional embedded palette]
[DATA — indexed pixels or animation rows]
[END — terminator]
Chunk headers and BHDR fields follow TEXBSI.
IFHD alone does not imply multiple frames. The four installed
sky textures have IFHD, a frame count of 1, and raw 256 by 256 indexed pixels.
The Glide sky uses the matching external COL palette, including index 0 as
an opaque color. General sprite decoding treats index 0 as transparent.