wai-rs: jpegai_pipeline::yuv_to_rgb / rgb_to_yuv — BT.709 colour combine #12
2026-07-14
wai-rs: jpegai_pipeline::yuv_to_rgb / rgb_to_yuv — BT.709 colour combine (float-exact)
The final pixel transform before the output image: BT.709 full-range YUV↔RGB, planes normalised to [0,1], chroma carrying the +0.5 offset. r = y + Kry·(v-½) ; b = y + Kby·(u-½) g = y - (Kb·Kby/Kg)·(u-½) - (Kr·Kry/Kg)·(v-½) (Kr,Kg,Kb,Kby,Kry = 0.2126, 0.7152, 0.0722, 1.8556, 1.5748) rgb_to_yuv is the exact inverse (for round-trip / re-encode). Validated against a BT.709-formula golden (max|Δ| = 1e-7) plus unit tests: greyscale (u=v=½ → r=g=b=y) and rgb→yuv→rgb round-trip identity to float precision. Co-Authored-By: Claude Opus 4.8 <[email protected]>