[argyllcms] Re: how to add patch around bw axis
- From: Nikolay Pokhilchenko <nikolay_po@xxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 31 Oct 2008 15:47:52 +0300
I've note, that addition of R=G=B patches isn't meant that there will be gray
patches at printer output, because of printer may be not linearized and
gray-balanced. The optimum way is the selection of wanted gray points in Lab,
then icclu conversion of this points to RGB data by preliminary profile. Of
course, RGB data may be converted to XYZ by icclu too.
As I wrote yesterday:
1. Computing LAB data array in table processor
2. Converting LAB array to RGB: icclu -fb -ir -s100 <LAB.txt >RGB.txt
PreProf.icc
3. Computing XYZ data for *.ti1: icclu -ff -ia -s100 <RGB.txt >XYZ.txt
4. Combining patch numbers, RGB and XYZ data in one table by table processor
5. Inserting this table into *.ti1 file.
You can't just add gray RGB by -g key because it changes OFP-spread in the
*.ti1 file, but You can generate separate file only with grays and combine two
ti1, one OFPS, one GRAYS into one big *.ti1 with "standard" OFPS and additional
grays.
I'd not recommend You to do regular gray spread across gray axis as in JPEGs
You shown. Randomized distribution may be more reasonable for profiling (ask
Graeme here).
See my MS Excel example how to add 101 Lab patches randomly placed in radius
7dE from gray axis.
-----Original Message-----
From: Daniele Pennati <danielepennati@xxxxxxxxxxxxx>
To: argyllcms@xxxxxxxxxxxxx
Date: Fri, 31 Oct 2008 08:59:56 +0100
Subject: [argyllcms] Re: how to add patch around bw axis
Thanks a lot for the answers!
I'm starting to understand how to add new patches.
But I don't want only to add gray patches (a can add these by the -g
command). I want to add also same gradients near to the gray axis...
something like what there is in the gretag target.
ATTACHMENT: image/jpeg (Cfrt_GrayAxis.jpg)
As you can see in the picture attached the gretag 288 patches target
(at right) has tre gradient (in the RGB directions) near to the gray
axis and the gretag 1100 patches target (at center) has six gradient
(in the RGB CMY directions) near to the gray axis.
Finally there is the PhotoActivity (an italian service) 1500 patches
target that has 6 gradient stratified in 4 level for each direction...
I built a tiff file with the patches like the photoactivity target and
I want to add these patches in the ti1 file (882 patches) made by
argyll... I have the rgb values expressed in 0-255 and I can convert
these values in 0-100 scale, but how can i get the xyz values?
thanks
Daniele
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