Free Lossless Image Format

The format was initially announced publicly in September 2015,

{{cite web

| title= Free Lossless Image Format (FLIF)

| date= 2015-09-06

| url= https://boards.openpandora.org/topic/18485-free-lossless-image-format-flif/

| archive-url= https://web.archive.org/web/20150912123111/http://boards.openpandora.org/topic/18485-free-lossless-image-format-flif/

| archive-date= 2015-09-12

}}

with the first alpha release occurring about a month later, in October 2015.

{{cite web

| title= Release v0.1-alpha

| date= 2015-10-03

| website= FLIF-hub/FLIF

| url= https://github.com/FLIF-hub/FLIF/releases/tag/v0.1-alpha

}}

The first stable version of FLIF was released in September 2016.

{{cite web

| title= Release v0.2

| date= 2016-09-22

| website= FLIF-hub/FLIF

| url= https://github.com/FLIF-hub/FLIF/releases/tag/v0.2

}}

For compression, FLIF uses MANIAC (Meta-Adaptive Near-zero Integer Arithmetic Coding), 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{{Cite web|url=https://flif.info/spec.html#_overview_of_the_format|title=FLIF16 Specification|website=flif.info|access-date=2019-11-28}} (unlike {{YCbCr}} that loses some color information to rounding errors, independently of its use in otherwise lossy JPEG). Not yet implemented are some features,{{Cite web|url=https://github.com/FLIF-hub/FLIF/issues/258|title = YCoCg Heuristics · Issue #258 · FLIF-hub/FLIF| website=GitHub }} e.g. other "color spaces (CMYK, YCbCr, ...)". The color space conversion is faster, but the overall decoding (and encoding) 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 (RGBA) like PNG (but unlike JPEG); and progressive coding, similar to PNG (unlike it, progressive compression doesn't increase file-size), but as FLIF's algorithm is more complex (and partly, may not have had as much tuning of the implementation yet), 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 tuning parameters which can result in differently sized images. All of the images are still lossless. A flifcrush tool is also available to achieve the minimal size.

Lossy compression can be achieved by preprocessing. The process is deterministic and does not cause generation loss.

File:UGUI FLIF screenshot.png]

• XnView supports FLIF since version 2.36.{{cite web|url=http://newsgroup.xnview.com/viewtopic.php?f=35&t=34085|title=XnView 2.39|author=Pierre-Emmanuel Gougelet|publisher=XnView|date=2016-11-08|access-date=2017-09-15}}
• ExifTool supports reading and writing metadata in FLIF images since version 10.31.{{cite web|url=http://owl.phy.queensu.ca/~phil/exiftool/ancient_history.html#v10.31|title=ExifTool Ancient History|author=Phil Harvey|publisher=ExifTool|date=2016-10-19|access-date=2017-11-01}}
• [https://flif.info/UGUI_FLIF/ UGUI-FLIF] supports preview and converting PNG file to FLIF.{{Cite web|url=http://flif.info/UGUI_FLIF/|title=UGUI: FLIF Download|website=flif.info|access-date=2018-12-27}}
• IrfanView supports reading FLIF images since version 4.52.{{Cite web|url=https://www.irfanview.com/main_history.htm|title=History of IrfanView Changes/Versions: [4.52 current 2018-12-12]|author=Irfan Skiljan|date=2018-12-12|access-date=2018-12-28}}{{Cite web|url=https://irfanview-forum.de/showthread.php?t=11867|title=IrfanView 4.52 has been released today -IrfanView Support Forum|author=Kuki Dent|date=2018-12-13|access-date=2018-12-28|archive-date=28 December 2018|archive-url=https://web.archive.org/web/20181228175001/https://irfanview-forum.de/showthread.php?t=11867|url-status=dead}}

{{Reflist|2}}

{{Portal|Free and open-source software}}

• {{Official website|http://flif.info|FLIF}} – official site
• {{GitHub|FLIF-hub/FLIF}}
• [https://github.com/UprootLabs/poly-flif PolyFLIF] – a Javascript library to decode FLIF in browsers
• {{openhub|FLIF|FLIF}}
• [http://github.com/sveinbjornt/Phew Phew] – native macOS FLIF viewer
• [https://supercompression.ru/ultra7z-flif-optimizer-eng FLIF Optimizer] – tuning parameters for better lossless compression

{{Graphics file formats}}

{{Compression formats}}

Category:Animated graphics file formats

Category:Graphics file formats

Category:Graphics standards

Category:Open formats

Category:Image compression