Pictures, palettes and fonts

FILEIO.C loads resources either from individual files or through an archive directory. Picture and palette loading share LOAD_PIC(). PICTURE.INC handles picture chunks and decoding; the graphics driver supplies scanline drawing and palette application.

File extensions alone do not identify the byte layout. Palette data can travel through the picture loader, and FONTS.CV contains the fonts used by the MCGA driver.

Screen-image encoding

IMAGE.C writes a rectangular page area through image_begin(), image_byte() and image_finish() in PICTURE.INC. Its run encoder uses escape byte 0x90:

• A literal 0x90 is written as 0x90, 0.
• A run of at least four equal non-escape bytes is written as value, 0x90, count, with count at most 255.
• Short remaining runs are written literally.

This describes the run layer. The assembly routines handle the surrounding stream encoding and framing, so these rules alone are not a complete PIC or MAP decoder.

Sprites and fonts

Pictures provide source pixels from which the game cuts sprites. In the MCGA driver a sprite stores width, height and rows trimmed of leading and trailing transparency. A row has a stored-pixel count, a leading transparent count, and its pixel bytes. Zero pixels are transparent when drawn.

FONTS.CV is appended to the driver’s data. The font table supplies offsets, metrics and glyph data, with a width table for proportional fonts. See the MCGA driver for the rendering calls.