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Introduction

Mission statement: OpenImageIO is a toolset for reading, writing, and manipulating image files of any image file format relevant to VFX / animation via a format-agnostic API with a feature set, scalability, and robustness needed for feature film production.

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, JPEG XL, 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.

🏢 Project administration and Licensing

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

For original code, we use the Apache-2.0 license, and for documentation, the Creative Commons Attribution 4.0 Unported License. In 2023 we asked historical users to relicense from the original BSD-3-clause license to Apache-2.0, and over 99.86% of lines of code have been relicensed to Apache-2.0. A small amount of code incorporated into this repository from other projects are covered by compatible third-party open source licenses.

The OpenImageIO project is part of the Academy Software Foundation, a part of the Linux Foundation formed in collaboration with the Academy of Motion Picture Arts and Sciences. The Technical Charter and Project Governance explain how the project is run, who makes decisions, etc. Please be aware of our Code of Conduct.

💁 User Documentation

OpenImageIO Documentation is the best place to start if you are interested in how to use OpenImageIO, its APIs, its component programs (once they are built). There is also a PDF version.

Additional resources:

• User quick start is a quick example of using OpenImageIO in Python, C++, and the command line.

👷 Building and installing OpenImageIO

• Build and installation instructions for OpenImageIO. Such as it is. This could use some work, particularly for Windows.

🚑 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"). For quick questions, you could also try the ASWF Slack #openimageio channel.

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 info@openimageio.org, or for security-related issues security@openimageio.org.

🔧 Contributing and developer documentation

OpenImageIO welcomes code contributions, and nearly 200 people have done so over the years. We take code contributions via the usual GitHub pull request (PR) mechanism.

• Architecture overview is a high-level description of the major classes and their relationships.
• CONTRIBUTING has detailed instructions about the development process.
• ROADMAP is a high-level overview of the current development priorities for the next annual release, expected in September, 2024.
• RELEASING explains our policies and procedures for making releases. We have a major, possibly-compatibility-breaking, release annually in September/October, and minor bug fix and safe feature addition release at the beginning of every month.
• Building the docs has instructions for building the documentation locally, which may be helpful if you are editing the documentation in nontrivial ways and want to preview the appearance.
• Other developer documentation is in the docs/dev directory.

☎️ Communications channels and additional resources

• Main web page
• GitHub project page
• Developer mail list
• ASWF Slack (look for the #openimageio channel)
• Biweekly Technical Steering Committee (TSC) Zoom meetings are on the ASWF Calendar (click on the OpenImageIO meeting entries, every second Monday, to get the Zoom link, anyone may join)