Free Lossless Image Format


Free Lossless Image Format is a lossless image format claiming to outperform PNG, lossless WebP, lossless BPG and lossless JPEG 2000 in terms of compression ratio on a variety of inputs.
FLIF supports a form of progressive interlacing with which any partial download of an image file can be used as a lossy encoding of the entire image.

History

The format was initially announced publicly in September 2015,
with the first alpha release occurring about a month later, in October 2015.
The first stable version of FLIF was released in September 2016.

Design

For compression, FLIF uses MANIAC, a variant of CABAC where the contexts are nodes of decision trees which are dynamically learned at encode time.
FLIF uses the reversible YCoCg color space. Not yet implemented are some features, e.g. other "color spaces ". The color space conversion is faster, but the overall decoding is still slower than it needs to be, or some of the competition, even with the better color space as that is only a small fraction of the overall process. The format supports an optional alpha channel like PNG ; and progressive coding, similar to PNG, but as FLIF's algorithm is more complex, it has a higher computational cost; at least lower bandwidth requirements can offset some of that extra time. Progressive coding reduces FLIF's performance.
FLIF supports grayscale, RGB and RGBA with color depth of 1 to 16 bits per channel.
FLIF has some parameters, and can result in differently sized images, with tuning, or done by flifcrush tool. All of those images are still lossless. FLYF, is also considered, and that would be the file-ending; while both could describe either and ending just used to indicate.

Support

supports FLIF since version 2.36.
ExifTool supports reading and writing metadata in FLIF images since version 10.31.
supports preview and converting PNG file to FLIF.
IrfanView supports reading FLIF images since version 4.52.