This repo implements illuminant estimation via Fast Fourier Color Constancy (FFCC) with C++ and Metal shaders. It's primarily a translation of the original MATLAB code to Metal.
This code is used by Photon's image pipeline to implement highlight reconstruction and white balancing.
See this blog post for more info about Photon's image pipeline.
The average time to process a single image (with the included example project) is ~1.9 ms on an Apple M3 MacBook Pro.
The performance could be improved further but effort hasn't been invested to do so because the existing performance is fine for Photon's needs.
See the Example directory for an example project that runs FFCC on some static images.
The FFCCModel::_F_fft0Vals and FFCCModel::_F_fft1Vals arrays are extracted from the MATLAB code after training on a set of images for the target image sensor.