The One Bit Image is a file format to store single bit depth
images, similar to 1-bit BMP files. It is a learning
adventure and does not aim to be ubiquitous or
well-performing. The name is shortened to obi, any files
that wish to be identified as this format may use the file
extension .obi, for example: apple.obi.
The file format consists of the following sections:
- File Header: 10 bytes, 0x0000 - 0x00A0
- Image Information Header: 16 bytes, 0x00A0 - 0x01A0
- Pixel data: Variable, 0x1A0 - Variable
This header contains the following metadata about the file itself:
- OBI version (2 bytes, 0x0000)
- File size in bytes (4 bytes, 0x0020)
- Data offset: Offset from the beginning of the file to the beginning of bitmap data (4 bytes, 0x0060)
This header contains metadata about the image:
- Width: Horizontal size of the bitmap data in pixels (4 bytes, 0x00A0).
- Height: Vertical size of the bitmap data in pixels (4 bytes, 0x00E0).
- Compression Algorithm: The following types of compression are supported: RLE, Kosinki etc. Set 0 if no compression (4 bytes, 0x0120).
- Image size after compression (set 0 if no compression, i.e., Compression=0). (4 bytes, 0x0160)
The image data. Each pixel is a single bit, the size of
Pixel Data is given by Width * Height.