[argyllcms] Re: Colprof feature request: amount of black pointhue correction control

I've checked several device data sets of RGB printers. The mapping techniqe of 
Argyll CMS is very good from Jab space point of view.
But my request still active. Take a look to .ti3 attached.

My test was:

colprof -nc -S"sRGB.icc" LSM2484

xicclu -fb -ir -pj -s255 LSM2484.icm
0 0 0 [Jab] -> Lut -> 21.542882 15.857801 0.000150 [RGB] (clip)

xicclu -ff -ia -pj -s255 LSM2484.icm
255 255 255 [RGB] -> Lut -> 92.590810 2.033623 -7.751497 [Jab]
0 0 0 [RGB] -> Lut -> 15.022740 -1.045231 -10.012886 [Jab]
21.542882 15.857801 0.000150 [RGB] -> Lut -> 16.663121 1.075238 -6.318114 [Jab]
Here we can see, that relative-mapped black point isn't so dark, as R=G=B=0, 
but the level of lightness is less, than the printer native tone shift 
compensated by mapping.
Let's check the perceptual intent:

xicclu -fb -ip -pj -s255 LSM2484.icm
0.000000 0.000000 0.000000 [Jab] -> Lut -> 4.710601 4.732119 0.000313 [RGB] 
(clip)

xicclu -ff -ia -pj -s255 LSM2484.icm
4.710601 4.732119 0.000313 [RGB] -> Lut -> 15.468991 -0.929117 -9.292939 [Jab]
0.000000 0.000000 0.000000 [RGB] -> Lut -> 15.022740 -1.045231 -10.012886 [Jab]

As in relative intent case, the "mapper" does it's work good - the shifted 
black point is slightly closer to white point, than native bp, but at the cost 
of less black lightness increase.
Generally, there are no any claims to "mapper", but the requested feature is 
needed for some special cases. For exaple text, artworks and other cases, where 
perceptual or relative color management is needed, but with accordance L=a=b=0 
to R=B=G=0.

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