Unusial MHC-profile behavior with special 1DLUT and XYZ->XYZ matrix

[dm-u]

Gradient in paint.net (non-color managed app).

MHC-profile with identity XYZ->XYZ matrix

$$\begin{bmatrix} 1 & 0 & 0 & 0 \\ 0 & 1 & 0 & 0 \\ 0 & 0 & 1 & 0 \end{bmatrix}$$

and 1DLUT [0, 1], [0.5, 0.5], [0, 1]. Gradient looks as expected:

MHC-profile with XYZ->XYZ matrix

$$\begin{bmatrix} 0.99 & 0 & 0 & 0 \\ 0 & 0.99 & 0 & 0 \\ 0 & 0 & 0.99 & 0 \end{bmatrix}$$

and 1DLUT [0, 1], [0.5, 0.5], [0, 1]. Something strange for low levels:

Closer:

Any ideas?

[dantmnf]

I have also reproduced this with an identity matrix on AMD GPU.

It seems this is driver-defined behavior and varies across GPU vendors.

P.S. Someone also reported that color (0, 0, 0) can't be transformed with MHC2 pipeline on NVIDIA GPU.