The BMP RLE 8 Compression Algorithm
--- BMP RLE_8 compression
The BMP can be compressed in two modes, absolute mode and RLE
mode. Both modes can occur anywhere in a single bitmap.
The RLE mode is a simple RLE mechanism, the first byte contains the
count, the second byte the pixel to be replicatet. If the count byte
is 0, the second byte is a special, like EOL or delta.
In absolute mode, the second byte contains the number of bytes to be
copied litteraly. Each absolute run must be word-aligned that means you
will may have to add an aditional padding byte which is not included
in the count. After an absolute run, RLE compression continues.
Second byte Meaning
0 End of line
1 End of bitmap
2 Delta. The next two bytes are the horizontal
and vertical offsets from the current position
to the next pixel.
3-255 Switch to absolute mode
This information is from Corion.net and is used with permission.