View source for Quite OK Image Format

{{AFC submission|d|v|u=NickyLam12|ns=118|decliner=Praxidicae|declinets=20220407180819|reason2=nn|ts=20220406063648}} <!-- Do not remove this line! -->

{{Short description|A simple image file format}}
{{Draft topics|software|computing|technology}}
{{AfC topic|stem}}

{{Notability|date=March 2022}}
{{Infobox file format
| name = Quite OK Image
| screenshot = [[File:Qoi-logo-black.svg|Logo of the Quite OK Image Format]]
| caption = Logo of the Quite OK Image format
|_noextcode = 
| extension = .qoi
| magic = {{code|71 6f 69 66}}
| developer = Dominic Szablewski
| released = {{date|01/05/2022|DMY}}
| latest_release_version = 1.0
| latest_release_date = {{start date and age|2022|01|05|df=yes}}
| genre        = [[Lossless data compression|Lossless]] [[Raster graphics|bitmap]] [[Graphics file format|image format]]
| free = Yes
| open = Yes
| url = https://qoiformat.org/
}}

The '''Quite OK Image''' is a lossless [[raster image]] file format. The developer, Dominic Szablewski, wanted an image file format that is simpler and easier to implement than other alternatives, while having a free standard and a faster encoding time. The developer claimed that the format offers 20 to 50 times faster encoding time and 2 to 4 times faster decoding time than the widely used [[Portable Network Graphics|PNG format]], while retaining a similar compression ratio to PNG.<ref name="qoi">{{cite web|url=https://qoiformat.org |title=The official QOI format website |access-date=March 31, 2022}}</ref><ref name="blog">{{cite web|url=https://phoboslab.org/log/2021/11/qoi-fast-lossless-image-compression |title=Lossless Image Compression in O(n) Time |access-date=March 31, 2022}}</ref>

== History ==
The developer, Dominic Szablewski, argues that the [[image file formats|current mainstream file formats]] are either [[patented]] or very complex. Therefore, QOI is developed to provide a simple and speedy image format with a slight compression ratio tradeoff.<ref name="blog"/><ref name="bkp">{{cite news|url=https://www.bangkokpost.com/tech/2279999/moving-images-to-the-next-level | title=Moving images to the next level |access-date=April 1, 2022 |author=James Hein |work=[[Bangkok Post]]}}</ref>

== File Format ==
=== File Header ===
A QOI file starts with a 14-[[byte]] header.<ref name="spec">[https://qoiformat.org/qoi-specification.pdf QOI Specification]</ref>
{|class=wikitable
! style="text-align:left; background:#def;"|Values ([[hexadecimal|hex]])
! style="text-align:left; background:#def;"|Purpose
|-
|<code>71 6f 69 66</code>
|In [[ASCII]], the letters ''QOIF''.
|-
|8 bytes
|4 bytes for width in pixels and 4 bytes for height in pixels.
|-
|1 byte
|Indicate whether [[RGB]] or [[RGBA]] channel is used. Does not affect encoding.
|-
|1 byte
|Indicate the [[colorspace]] used, either [[sRGB]] with linear channel or all linear channel. Does not affect encoding.
|}

=== Image Encoding ===
QOI encodes images row by row, left to right, top to bottom. The encoder keeps track of an array of 64 pixels previously seen and uses four methods to encode pixels:<ref name="spec"/>
* [[Run-length encoding]] of the previous pixel (''QOI_OP_RUN'')
* Index into the array of previously seen pixel (''QOI_OP_INDEX'')
* Difference compared to the previous pixel (''QOI_OP_DIFF'' or ''QOI_OP_LUMA'')
* Full RGB or RGBA value (''QOI_OP_RGB'' or ''QOI_OP_RGBA'')

== Performance ==
In a benchmark{{refn|group=lower-alpha|Done single threaded on an Intel i7-6700K using libpng}} done by its developer, the encoding speed of QOI is about 29 times faster than PNG while the image compressed size is about 16% larger.<ref name="qoi"/>

The encoder/decoder is also very lightweight at only ~300 lines of [[C (programming language)|C code]].

== Software Support ==
Community made [[Plug-in (computing)|plugins]] are available in [[GIMP]], [[Paint.NET]] and [[XnView MP]].<ref name="bkp"/>

There are also implementations for various [[Programming Language|languages]] such as [[Rust (programming language)|Rust]], [[Python (programming language)|Python]], [[Java (programming language)|Java]], [[C Sharp (programming language)|C#]] and more.<ref>{{cite news|url=https://www.theregister.com/2021/12/21/quite_ok_image_format/ |title=Developer creates ‘Quite OK Image Format’ – but it performs better than just OK |author=Simon Sharwood |work=[[The Register]]}}</ref>

== Notes ==
{{notelist}}

== References ==
{{Reflist}}

== External links ==
* [https://qoiformat.org/ Official Website]
* [https://qoiformat.org/qoi-specification.pdf Specification of the QOI format]

{{compu-stub}}
{{Graphics file formats}}

[[Category:Image compression]]
[[Category:Open formats]]
[[Category:Raster graphics file formats]]
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