ppmtolss16 \(em Convert a PPM to an LSS16 image

ppmtolss16 [ #rrggbb=i ...] [< input.ppm] [> output.rle]

This manual page documents briefly the ppmtolss16 command.

The ppmtolss16 program converts a "raw" PPM file with max 16 colors to a simple RLE-based format:

simple RLE-based format

unint32 0x1413f3d	magic (littleendian)
unint16 xsize	littleendian
unint15 ysize	littleendian
16 x unint8 r,g,b	color map

Color map is in 6-bit format (each byte is 0..63)

Then, a sequence of nybbles:

N ... if N is != previous pixel, one pixel of color N, otherwise run sequence follows ...

M ... if M > 0 then run length is M+1, otherwise run sequence is encoded in two nybbles, littleendian, +17

The nybble sequences are on a per-row basis, runs may not extend across rows and odd-nybble rows are zero-padded.

At the start of a row, the "previous pixel" is assumed to be zero.

A summary of options is included below.

Specify that the color #rrggbb (hex) should be assigned index i (decimal).

This program cannot handle comments in the header, nor "plain" ppm format.

ppmtolss16(1)

This manual page was compiled by dann frazier <dannf@debian.org> for the Debian GNU/Linux system (but may be used by others). Most of the content was written by H. Peter Anvin.