GD

gd, also known as libgd, is an open-source graphics library written in C that provides facilities for creating and manipulating bitmap images dynamically. It is designed to be embedded in applications and used to generate images on the fly, such as on web servers or in utility programs.

The library offers a rich API for image creation and manipulation. It supports drawing primitives (lines, polygons, shapes), text rendering with both bitmap and TrueType fonts, color allocation and management, and image transformations such as resizing, rotating, and filtering. It also provides support for image formats commonly used on the web, including PNG, JPEG, GIF, WebP, as well as several others like BMP and TIFF. Truecolor support and alpha transparency are available, enabling more sophisticated image effects and compositing.

gd is widely used in practice through its role in the PHP language, where the GD extension exposes its functions to generate and manipulate images on the server. Beyond PHP, libgd has bindings or usage in various other programming languages and projects, making it a common choice for dynamic image generation in different ecosystems.

History and licensing: libgd has been developed since the 1990s and has seen continual updates to add formats, color modes, and performance improvements. It is distributed as free/open-source software under a permissive license, making it suitable for use in both open-source and proprietary software. The library's ongoing development is coordinated by its community and maintainer teams, who release new versions and enhancements.