qoi

The “Quite OK Image Format” for fast, lossless image compression

phoboslab
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C

QOI Logo

QOI - The “Quite OK Image Format” for fast, lossless image compression

Single-file MIT licensed library for C/C++

See qoi.h for
the documentation and format specification.

More info at https://qoiformat.org

Why?

QOI offers sweet-spot of compression ratio and throughput for lossless
image encoding. QOI’s compression is roughly comparable to PNG (usually worse than
libPNG, but better than stb_image_write.h), while throughput is a lot higher.

Benchmark results on a few thousand images can be found here: https://qoiformat.org/benchmark/

The QOI format is also extremely simple, which helps a lot when porting to other languages.

Example Usage

  • qoiconv.c
    converts between png <> qoi
  • qoibench.c
    a simple wrapper to benchmark stbi, libpng and qoi

MIME Type, File Extension

The recommended MIME type for QOI images is image/qoi. While QOI is not yet
officially registered with IANA, I believe QOI has found enough adoption to
prevent any future image format from choosing the same name, thus making a
MIME type collision highly unlikely (see #167).

The recommended file extension for QOI images is .qoi

Limitations

The QOI file format allows for huge images with up to 18 exa-pixels. A streaming
en-/decoder can handle these with minimal RAM requirements, assuming there is
enough storage space.

This particular implementation of QOI however is limited to images with a
maximum size of 400 million pixels. It will safely refuse to en-/decode anything
larger than that. This is not a streaming en-/decoder. It loads the whole image
file into RAM before doing any work and is not extensively optimized for
performance (but it’s still very fast).

If this is a limitation for your use case, please look into any of the other
implementations listed below.

Improvements, New Versions and Contributing

The QOI format has been finalized. It was a conscious decision to not have a
version number in the file header. If you have a working QOI implementation today,
you can rest assured that it will be compatible with all QOI files tomorrow.

There are a lot of interesting ideas for a successor of QOI, but none of these will
be implemented here. That doesn’t mean you shouldn’t experiment with QOI, but please
be aware that pull requests that change the format will not be accepted.

Likewise, pull requests for performance improvements will probably not be accepted
either, as this “reference implementation” tries to be as easy to read as possible.

Tools

Implementations & Bindings of QOI

QOI Support in Other Software

  • Amiga OS QOI datatype - adds support for decoding QOI images to the Amiga operating system.
  • SerenityOS - supports decoding QOI system wide through a custom cpp implementation in LibGfx
  • Raylib - supports decoding and encoding QOI textures through its rtextures module
  • Rebol3 - supports decoding and encoding QOI using a native codec
  • c-ray - supports QOI natively
  • SAIL - image decoding library, supports decoding and encoding QOI images
  • Orx - 2D game engine, supports QOI natively
  • IrfanView - supports decoding and encoding QOI through its Formats plugin
  • ImageMagick - supports decoding and encoding QOI, since 7.1.0-20
  • barebox - bootloader, supports decoding QOI images for splash logo, since v2022.03.0
  • KorGE - & KorIM Kotlin 2D game engine and imaging library, supports decoding and encoding QOI natively since 2.7.0
  • DOjS - DOS JavaScript Canvas implementation supports loading QOI files
  • XnView MP - supports decoding QOI since 1.00
  • ffmpeg - supports decoding and encoding QOI since 5.1
  • JPEGView - lightweight Windows image viewer, supports decoding and encoding of QOI natively, since 1.1.44
  • darktable - photography workflow application and raw developer, supports decoding since 4.4.0
  • KDE - supports decoding and encoding QOI images. Implemented in KImageFormats
  • EFL - supports decoding and encoding QOI images since 1.27.
  • Swingland - supports QOI decoding/loading via the ImageIO API of this Java Swing reimplemenation for Wayland
  • Imagine - supports decoding and encoding QOI images since 1.3.9
  • Uiua - supports decoding and encoding QOI images since 0.8.0
  • Google Earth Pro - supports Movie Maker export as sequence of QOI images since 7.3.6

Packages

  • AUR - system-wide qoi.h, qoiconv and qoibench install as split packages.
  • Debian - packages for binaries and qoi.h
  • Ubuntu - packages for binaries and qoi.h

Packages for other systems tracked at Repology.