Code Quality Rank: L1
Programming language: C++
License: Apache License 2.0
Tags: Image Processing    
Latest version: v2.3.1.1

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README for OpenImageIO

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The primary target audience for OIIO is VFX studios and developers of tools such as renderers, compositors, viewers, and other image-related software you'd find in a production pipeline.

OpenImageIO consists of:

  • Simple but powerful ImageInput and ImageOutput APIs that provide an abstraction for reading and writing image files of nearly any format, without the calling application needing to know any of the details of these file formats, and indeed without the calling application needing to be aware of which formats are available.

  • A library that manages subclasses of ImageInput and ImageOutput that implement I/O from specific file formats, with each file format's implementation stored as a plug-in. Therefore, an application using OpenImageIO's APIs can read and write any image file for which a plugin can be found at runtime.

  • Plugins implementing I/O for several popular image file formats, including TIFF, JPEG/JFIF, OpenEXR, PNG, HDR/RGBE, ICO, BMP, Targa, JPEG-2000, RMan Zfile, FITS, DDS, Softimage PIC, PNM, DPX, Cineon, IFF, OpenVDB, Ptex, Photoshop PSD, Wavefront RLA, SGI, WebP, GIF, DICOM, HEIF/HEIC/AVIF, many "RAW" digital camera formats, and a variety of movie formats (readable as individual frames). More are being developed all the time.

  • Several command line image tools based on these classes, including oiiotool (command-line format conversion and image processing), iinfo (print detailed info about images), iconvert (convert among formats, data types, or modify metadata), idiff (compare images), igrep (search images for matching metadata), and iv (an image viewer). Because these tools are based on ImageInput/ImageOutput, they work with any image formats for which ImageIO plugins are available.

  • An ImageCache class that transparently manages a cache so that it can access truly vast amounts of image data (tens of thousands of image files totaling multiple TB) very efficiently using only a tiny amount (tens of megabytes at most) of runtime memory.

  • A TextureSystem class that provides filtered MIP-map texture lookups, atop the nice caching behavior of ImageCache. This is used in commercial renderers and has been used on many large VFX and animated films.

  • ImageBuf and ImageBufAlgo functions -- a simple class for storing and manipulating whole images in memory, and a collection of the most useful computations you might want to do involving those images, including many image processing operations.

  • Python bindings for all of the major APIs.


OpenImageIO is (c) Copyright Contributors to the OpenImageIO project.

OpenImageIO is distributed using the [modified BSD license](LICENSE.md) (also known as the "new BSD" or "3-clause BSD" license). The documentation is licensed under the Creative Commons Attribution 3.0 Unported License.

The plain English bottom line is that OpenImageIO is free, as well as freely modifiable and redistributable (in both source and binary form). You may use part or all of it in your own applications, whether proprietary or open, free or commercial. Using it in a commercial or proprietary application DOES NOT obligate you to pay us, or to use any particular licensing terms in your own application.

Some code and resources are distributed along with OIIO that have highly compatible, though slightly different, licenses (generally MIT or Apache). See the PDF documentation Acknowledgements section, and the [THIRD-PARTY](THIRD-PARTY.md) file for details.

Building and Installation

Please read the [INSTALL.md](INSTALL.md) file for detailed instructions on how to build and install OpenImageIO.

If you build with EMBEDPLUGINS=0, remember that you need to set the environment variable OIIO_LIBRARY_PATH to point to the 'lib' directory where OpenImageIO is installed, or else it will not be able to find the plugins.


The primary user and programmer documentation can be found on openimageio.readthedocs.io as html or as PDF.

Contact & reporting problems

Simple "how do I...", "I'm having trouble", or "is this a bug" questions are best asked on the oiio-dev developer mail list. That's where the most people will see it and potentially be able to answer your question quickly (more so than a GH "issue").

Bugs, build problems, and discovered vulnerabilities that you are relatively certain is a legit problem in the code, and for which you can give clear instructions for how to reproduce, should be reported as issues.

If confidentiality precludes a public question or issue, you may contact us privately at [[email protected]]([email protected]), or for security-related issues [[email protected]]([email protected]).


OpenImageIO welcomes code contributions, and [nearly 150 people](CREDITS.md) have done so over the years. We take code contributions via the usual GitHub pull request (PR) mechanism. Please see [CONTRIBUTING](CONTRIBUTING.md) for detailed instructions.

Web Resources

*Note that all licence references and agreements mentioned in the OpenImageIO README section above are relevant to that project's source code only.