A raw image is a simple bitmap format containing pixels described as a single byte each, from left to right and row by row from the top to the bottom. Each pixel's value corresponding to its palette index, so the format is limited to 256 colors. Translucency is not supported. The format contains no header and no palette information; the engine has to know how to interpret them correctly through other means. This is done by simply looking at the total size and checking if it is a known acceptable size or not.
All Doom-engine games uses this format for flats, which are 4096-byte lumps interpreted as 64x64, though ZDoom also supports 64x128 (Hexen variant, 8192 bytes), 128x128 (15384 bytes), and 256x256 (65536 bytes).
In addition to flat, the following lumps are raw images, and 320×200 unless specified otherwise:
- Both Raven games
- TITLE, HELP1, HELP2 and CREDIT have normal size. AUTOPAGE, a 320x158 graphic; though ZDoom will accept any height (any size that's a multiple of 320, not necessarily 50560 bytes).
- FINAL1, FINAL2 and E2END; the latter is notable as a special case because it uses the E2PAL palette instead of PLAYPAL.
- INTERPIC, FINALE1, FINALE2 and FINALE3.
- STARTUP0; STRTLZ1 and STRTLZ2 (16×16, 256 bytes); STRTBOT (48×48 picture, 2304 byte); STRTPA1, STRTPB1, STRTPC1 and STRTPD1 (32×64 picture, 2048 bytes), all of which are startup lumps.