WOBA
The WOBA format was used inside a HyperCard stack to store black-and-white bitmap images using a form of lossless compression invented by Bill Atkinson. The format has no formal name; the name WOBA was given to the format by the lead developers of Project 11, an attempt at a HyperCard clone, in the early 2000s. The name WOBA stands for "Wrath of Bill Atkinson" and was inspired by the complexity and non-obviousness of the compression algorithm.
The WOBA format was never used outside of HyperCard, so any instances of a WOBA image by itself were most likely extracted from a HyperCard stack as part of a reverse-engineering effort. An extracted WOBA image usually includes the block header from the HyperCard stack format to make it easily identifiable.
References
- The Definitive Guide to the HyperCard Stack File Format describes the WOBA format in the section on the BMAP block
- PowerPaint can read and write WOBA image files
