OpenCV

OpenCV, maintained by the non-profit Open Source Vision Foundation since 2000, is a free, open-source computer vision library with over 2,500 algorithms for image/video processing, object detection, face recognition, and deep learning workflows. It offers C++, Python, and Java interfaces across Linux, macOS, Windows, iOS, and Android, and is licensed under Apache 2 — free for commercial use with no royalties. The foundation itself generates revenue separately through OpenCV University courses, an annual AI competition, and consulting via OpenCV.AI, rather than through the library. As a low-level computer-vision library, it requires real programming ability to use directly; it's infrastructure for developers building CV applications, not an end-user tool. Being two decades old and still actively releasing (recent blog posts, ongoing competitions) is itself a strong signal of durability rare among AI tools. Good fit for a developer building any application that needs image or video analysis — object detection, face recognition, or custom computer-vision pipelines.