QOI, the Quite OK Image Format, added to GID, the Generic Image Decoder
QOI (the Quite OK Image Format, home page here) is a very simple raster image format with a decent lossless compression and an extremely good performance - a direct consequence of its simplicity and its compression features.
It was clear from the first sight on that format that it was urgent to add it to GID, the Generic Image Decoder 😎. GID is free, open-source, available on SourceForge here and GitHub here.
Here, a few examples of QOI test images decoded by GID (with its default background for transparency):
The cool ideas in the QOI format are
- a "moving palette" - a list of recently shown colours, that is updated during the encoding or decoding of the pixels; the indexing is done with a hash function
- a shortcut encoding for slightly different colours from a pixel to the next
- a shortcut encoding for slightly different brightness from a pixel to the next.
Transparency, in the form of levels from 0 to 255, (the alpha channel) is supported.
Add to it a run-length encoding that fits well surfaces with identical colours and transparency, and the format remains so simple that you can squeeze its detailed specification on a single, readable, A4 page!
|Click to enlarge|