Imagine is a PHP library for image manipulation providing a unified API over GD, Imagick, and Gmagick extensions. It offers a rich set of features including resizing, cropping, rotating, effects, drawing, filters, color management, metadata reading, and layered image support. The library is well-architected with clean interfaces, abstract base classes, and a factory pattern that allows swapping drivers. It includes extensive test coverage with reusable test infrastructure. While primarily a library, it is a mature, actively maintained solution for PHP image processing.