Semi Advanced Compression subtypes for 24 and 32 bit MBM image formats (4,2 and 5,3 - see MBM.TXT for details).

These compressions are more sophisticated than the basic ones described in the MBM.txt file thus description will be longer and that's why it s placed in separate file. These sub-format compression types are still relatively simple and for any input data there is only one possible optimal compressed sequence when using these compression subtypes.


With these compression types pixel data can be either in compressed or non-compressed blocks.

Byte 0 indicates start of compressed sequence, following with color bytes for pixel in current location (r,g,b for 24-bit type and t,r,g,b gor 32-bit type), following with one byte offset values indicating pixel of the same color. Each offset value is an offset from the last offset. Two offset values have special meaning. Value 0 indicates end of current compressed block, and value 255 indicates that there is a sequence of pixels of same color, one after other. If oldest bit of next byte after 255 is 0 then the byte is (number-2) of repeating pixels. If oldest bit of next byte after 255 is 1 then its remaining 7 bits are the oldest bits of a 15-bit number, youngest 8-bits of that number are in following byte. These 15 bits are (number-130) of repeating pixels.

Byte different than 0 indicates start of uncompressed sequence. The byte's value is the length of the sequence, i.e. number of following pixels (r,g,b sequences for 24-bit format and t,r,g,b sequences for 32-bit format).


Last revision: 9 October 2012

The actual (up-to-date) copy of this file can be found at http://www.4neurons.com/other/mbm/MBM-SAC.txt
The actual MBM image format specification, this file provides details for, can be found at http://www.4neurons.com/other/mbm/MBM.TXT