WHT is essentially a cheap implementation of multi-dimensional DCT, so it approximates but doesn't actually replace DCT in all scenarios. It seems that DCT is a

WHT is essentially a cheap implementation of multi-dimensional DCT, so it approximates but doesn't actually replace DCT in all scenarios. It seems that DCT is a better fit for photographic contents than WHT but was more expensive until FP multiplication became much cheaper so WHT was briefly considered as an alternative.