.NEO File Format

Introduction

NEOchrome was a paint program from Atari for the Atari ST, given away in the machine’s early years. Its .neo files hold one full screen in low resolution, 320 × 200 pixels in 16 colours, and many games and demos of the time kept their graphics in this format.

NEOchrome could animate a picture by cycling a range of palette colours, and the file keeps the settings for that alongside the image.

Structure

A NEOchrome file is always 32128 bytes: a 128-byte header and then 32000 bytes of screen memory, uncompressed, with the bitplanes interleaved word by word as the ST shows them. All values are big-endian.

The header starts with a flag word, normally 0, and a resolution word (0 for low resolution). The 16 palette words follow, then a 12-byte file name and the colour cycling settings: the range of colours, the speed and the number of steps. The rest of the header is reserved.

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