Contributing to libjpeg-turbo ============================= libjpeg-turbo is a stable and mature product with a worldwide reach, it is an ISO/ITU-T reference implementation of the JPEG standard, and its maintainer does not earn a salary for maintaining it. Thus, not every code contribution can or will be accepted into the libjpeg-turbo code base. In order to maximize the chances that a code contribution is acceptable, please adhere to the following guidelines: 1. If the code contribution is a bug fix, then please ensure that enough information is provided so that the maintainer can readily reproduce and document the bug. That information should include: - A clear and concise description of the bug - The steps and (if applicable) images necessary to reproduce the bug - The compilers, operating systems, and CPUs with which the bug was observed - The versions of libjpeg-turbo with which the bug was observed - If the bug is a regression, the specific commit that introduced the bug (use `git bisect` to determine this) 2. If the code contribution will implement a major new feature, then please contact the project maintainer (through a [GitHub issue](https://github.com/libjpeg-turbo/libjpeg-turbo/issues/new), [direct e-mail](https://libjpeg-turbo.org/About/Contact), or the [libjpeg-turbo-devel mailing list](https://libjpeg-turbo.org/About/MailingLists)) prior to implementing the feature. In general, major new features that are potentially disruptive to the quality of libjpeg-turbo are unlikely to be accepted unless: - The new feature is within the existing scope of libjpeg-turbo. - The new feature has been thoroughly regression tested and benchmarked on all of the supported platforms that are potentially affected by it. - The new feature has been documented clearly and concisely in the change log and (if applicable) the libjpeg and TurboJPEG API documentation and man pages. - The code implementing the new feature is formatted consistently with the rest of the libjpeg-turbo code base. (Use [checkstyle](https://github.com/libjpeg-turbo/checkstyle) to validate this.) - The new feature does not introduce new members into the exposed libjpeg API structures. (Doing so would break backward ABI compatibility.) - The new feature does not alter existing libjpeg-turbo usage or development workflows. - The code implementing the new feature is elegant, easily maintainable, and causes the least possible amount of disruption to the libjpeg-turbo code base. - The new feature is based on the dev branch of the libjpeg-turbo repository. ... OR ... - Your organization is prepared to pay for the labor necessary to ensure all of the above. Even the most well-written patches can still require a significant amount of labor to clean up, test, and integrate. (See above RE: the maintainer not earning a salary.) Specific types of features that *will not* be accepted: - Features that extend the scope of libjpeg-turbo to support image formats other than DCT-based and lossless JPEG and JFIF - Features that extend the scope of libjpeg-turbo to support image processing algorithms that are not necessary for JPEG compression or decompression - Extensions to the JPEG format that have not been approved by the appropriate standards bodies - Non-trivial performance enhancements that have less than a 5% overall impact on performance 3. If the code contribution is a build system enhancement, then please be prepared to justify the enhancement. In general, build system enhancements are unlikely to be accepted unless: - The enhancement is potentially beneficial to a significant number of upstream libjpeg-turbo users/developers. (If the enhancement is only beneficial to a downstream project, then it does not belong here.) - The enhancement has been tested with the following CMake versions: - The earliest version of CMake that libjpeg-turbo currently supports (refer to CMakeLists.txt) - The most recent major version of CMake - (if applicable) The earliest version of CMake with which the enhancement can be used - The enhancement has been tested on all of the major platforms (Mac, Un*x, Windows/Visual C++, Windows/MinGW) that are potentially affected by it. - The enhancement does not introduce new build system requirements or CMake variables unless absolutely necessary. - The enhancement does not alter existing libjpeg-turbo development workflows. Specific types of build system enhancements that *will not* be accepted: - Enhancements that allow libjpeg-turbo to be built from a subdirectory of a downstream repository. These enhancements are not maintainable in the upstream libjpeg-turbo build system. Use the CMake `ExternalProject_Add()` function instead. - Enhancements that introduce new (non-CMake-based) build systems Pull Requests ------------- This project does not allow unsolicited pull requests. If, after discussing a proposed code contribution with the project maintainer, a pull request is warranted, then you will be given access to the pull request system. Use of AI --------- No code or other content in the libjpeg-turbo source tree was generated, in whole or in part, using AI tools. Because it is impossible to know what source material was used to train a particular AI model, it is impossible to know whether placing AI-generated code and other content under libjpeg-turbo's open source licenses would violate someone else's copyright. At best, it is a legal gray area. For that reason and others, this project does not accept any contributions intended for inclusion in the libjpeg-turbo source tree that were generated, in whole or in part, using AI tools.