Indeed, degree-4 rational polynomials are generally enough for JPEG XL. Code for evaluating them using Horner's scheme (just FMAs): https://github.com/libjxl/li

Indeed, degree-4 rational polynomials are generally enough for JPEG XL. Code for evaluating them using Horner's scheme (just FMAs): https://github.com/libjxl/libjxl/blob/bdde644b94c125a15e532b2572b96306371a7d4e/lib/jxl/rational_polynomial-inl.h https://github.com/libjxl/libjxl/blob/bdde644b94c125a15e532b... I initially used Chebfun to approximate them, then a teammate implemented the same Caratheodory-Fejer method in C. We subsequently convert from Chebyshev basis to monomials. Blog sounds good :)