Separations output format
Separations output format is a raster picture file format using subtractive colours. It can only store one page, but it it can encode up to 255 separations, with the names of the separations included in the file, and supports up to sixteen bits per channel. Metadata (such as resolution, page numbers, etc) can also be optionally recorded.
Currently, the only known program that uses this format is TeXnicard, whose source code repository includes the documentation of this file format.
The file starts with seven ASCII characters SepOutF and then the next byte has a value of one (the ASCII "start of header" control code).