Chris Newman <
mec@npost.uk> wrote:
In article <mpro.sbc3nn00njemc05cj.news@stevefryatt.org.uk>, Steve Fryatt <news@stevefryatt.org.uk> wrote:
On 2 Apr, Harriet Bazley wrote in message
<6d006c4b5b.harriet@bazleyfamily.co.uk>:
The colour picker allows you to switch between RGB, CMYK and HSV
values and translates the current setting as you do so
If you want a stand-alone version, Rosemary Miskin's ColDef2 would
probably do the trick.
https://miskin.orpheusweb.co.uk/net/main2.html
That leads me to version 1.26 (2006). I discovered sitting n my machine I already have 1.30 (2023). From whence that cometh I know not.
I was trying to help the mem sahib who was using MS Publisher. she had concocted a yellow which according to her m/c had the values R 255 G 252 B
0
Putting that into an online converter gave C 0 M 1 Y 80 K 0
Another converter gave the CMYK in percentages ie
C 0 M 1.18 Y 100 B 0
Putting that into paint gave percentages.
R 100 G 98.8 B 20 Tried again and got R 94.9 G 93.7 B 14.9
ColDef2 gave R 87.1 G 85.9 B 7
So something is being lost in the translation.
Yes, that is unavoidable. There are many ways of converting both ways and
you cannot generally expect a round-trip to get you back to where you
started from, nor can you expect that a colour in one colour space even has
a matching colour in the other.
The way an RGB colour looks depends on your monitor and its settings and the way a CMYK colour looks depends on the ink and paper used for printing. To
get an accurate conversion, you need a process called colour management involving a calibrated monitor and colour profiles.
The RGB<->CMYK conversion done by the RISC OS colour picker is extremely simplistic and not really usable for defining colours for professional print work. Some applications, e.g., OvationPro and ArtWorks (with CMYK ink simulation switched on) do slightly better, but this is still very far from even the beginnings of a colour managed workflow.
In the absence of a fully colour managed workflow your best bet is to go to
the printers and look at printed samples of standard colour palettes, e.g., Pantone and choose one of these colours. If you then put the CMYK values
given for the chosen colour into an application that can deal with CMYK
colours and you have an output process that gets them to the printers
without them being converted back to RGB on the way, then you have a chance that the correct colour will eventually appear in the printed output.
--
Martin Wuerthner MW Software
http://www.mw-software.com/
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