luttex = PsychHelperCreateGenericLuminanceToRGBA8LUT(lut);
Helper function for PsychImaging() - Don’t call from usercode!
Used by PsychImaging(….,’EnableGenericHighPrecisionLuminanceOutput’, lut);
Converts a luminance -> RGB8 or RGBA8 LUT as provided in the 3- or 4 rows
by n columns matrix ‘lut’ into an equivalent RGBA8 lookup table texture,
then returns the texture handle to the calling routine.
‘lut’ = 3 rows by nslots columns uint8 matrix for LUT’s that map the
input luminance value range [0.0 - 1.0] to the integral 0 - nslots range,
then lookup the corresponding RGB8 output pixel in the lut. If ‘lut’ has
4 rows, then the 4th row encodes alpha-channel - This is only useful for
debugging, as teh alpha channel can’t be output to the external device.
The lut texture is built as a 256x256 2D rectangle texture, allowing for
luts with up to 2^16 luminance slots that work on all supported graphics
hardware. One could extend the size of the texture to up to 8192x8192 on
latest hardware, allowing for up to 2^26 bits, but that is likely not
that useful, given that internal GPU precision is restricted to 23 bits
(floating point single precision) and there doesn’t exist a single output
device with more than 16 bits of output resolution anyway.