Corrected the ordering of the real transform operators. The transform was invertible before, but it wasn't filtering correctly. This was a result of doing the real transform after the full 2D operator. The real transform must be paired with the associated FFT. And, the inverse transform operators must be in the mirror order. Basically, real transform operators and FFT operators do not commute. The correct order is
FFT cols
RFT
FFT rows
[Filter]
IFFT rows
IRFT
IFFT cols
Merge branch 'master' of https://github.com/willtalmadge/Image-Shader