GPUImage 3 is the third generation of the GPUImage framework, an open source project for performing GPU-accelerated image and video processing on Mac and iOS. The original GPUImage framework was written in Objective-C and targeted Mac and iOS, the second iteration rewritten in Swift using OpenGL to target Mac, iOS, and Linux, and now this third generation is redesigned to use Metal in place of OpenGL. The objective of the framework is to make it as easy as possible to set up and perform realtime video processing or machine vision against image or video sources. Previous iterations of this framework wrapped OpenGL (ES), hiding much of the boilerplate code required to render images on the GPU using custom vertex and fragment shaders. This version of the framework replaces OpenGL (ES) with Metal. Largely driven by Apple's deprecation of OpenGL (ES) on their platforms in favor of Metal, it will allow for exploring performance optimizations over OpenGL and a tighter integration with Metal-based frameworks and operations.