FLIF stands for Free Lossless Image Format. Can also do LossY (FLYF)
According to the compression experiments they have performed, FLIF files are on average:
- 14% smaller than lossless WebP,
- 22% smaller than lossless BPG,
- 33% smaller than brute-force crushed PNG files (using ZopfliPNG),
- 43% smaller than typical PNG files,
- 46% smaller than optimized Adam7-interlaced PNG files,
- 53% smaller than lossless JPEG 2000 compression,
- 74% smaller than lossless JPEG XR compression.
Even if the best image format was picked out of PNG, JPEG 2000, WebP or BPG for a given image corpus, depending on the type of images (photograph, line art, 8 bit or higher bit depth, etc), then FLIF still beats that by 12% on a median corpus (or 19% on average, including 16-bit images which are not supported by WebP and BPG). Thus FLIF is the best lossless format for any image type, bar none. The user does not need to mess with parameters to improve compression, unlike PNG.
The latest stable version is FLIF16
- Lossless compression
- Lossy compression (encoder preprocessing option, format itself is lossless so no generation loss)
- Grayscale, RGB, RGBA (also palette and color-bucket modes)
- Color depth: up to 16 bits per channel (high bit depth, HDR)
- Interlaced (default) or non-interlaced
- Interlaced files can be decoded quickly at lower quality/resolution (“Responsive By Design”)
- Progressive decoding of partially downloaded files
- Animation support
- Support for embedded ICC Profiles, Exif and XMP metadata
- Rudimentary support to compress camera raw files (RGGB)
- Encoding and decoding speeds are acceptable, but should be improved
 Other features
Progressive and lossless - FLIF is lossless, but can still be used in low-bandwidth situations, since only the first part of a file is needed for a reasonable preview of the image.
Responsive by design - A FLIF image can be loaded in different ‘variations’ from the same source file, by loading the file only partially. This makes it a very appropriate file format for responsive web design.
Free - No patents, no royalty fees
Free Lossy File format. One of the advantages of using a lossless format in a lossy way (as opposed to using a lossy format), is that generation loss is not an issue. Of course the information that is lost, stays lost, but no matter how many times you save a FLIF file, it will not get any additional loss from a decode-encode cycle. This is not the case for e.g. JPEG, where each decode-encode cycle always introduces additional loss.