Colormanagement

Colormanagement

[Jan U. Hasecke]

Hi all,

I defined some colors with \definecolor like this:

\definecolor [myblue] [r=0.000, g=0.314, b=0.580, c=0.98,  m=0.67,
y=0.03, k=0.12]

\startnotmode[print]
\setupcolors[cmyk=no,rgb=yes]
\stopnotmode

\startmode[print]
\setupcolors[cmyk=yes,rgb=no]
\setupbackend[
	format=PDF/X-3:2003,
   intent={ISO Coated v2 300\letterpercent\space (ECI)},
   ]
\stopmode

When I use "context" or "context --mode=print" everything works as expected.

But! I have SVG icons I want to use in the document. They contain the
above defined rgb colors.

When I use --mode=print I get different colors for the SVG icons.

So context converts the SVG files to PDFs but does not change the colors
accordingly to CMYK.

What are my options? Do I miss something?

1. Let the designer produce icons in pdf with the given cmyk colors.

2. Don't use cmyk colors at all.

In fact on my home printer the printed rgb colors look brighter than the
cmyk colors. This might change in the print shop when they print with
the right color profile, but it makes me nervous.

juh


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___________________________________________________________________________________

Re: Colormanagement

[Hans Hagen]

On 11/9/2018 4:24 PM, Jan U. Hasecke wrote:

> So context converts the SVG files to PDFs but does not change the colors
> accordingly to CMYK.
i don't know if inkscape has a switch for conversion

Hans

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                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
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Re: Colormanagement

[Tomas Hala]

Hi, 

by default, really not.

At http://wiki.inkscape.org/wiki/index.php/Color_management
and http://wiki.inkscape.org/wiki/index.php/ExportPDFCMYK
there some instructions how to convert files to CMYK,
or how to install some extension, respectively.
But I have not test these ways yet.

Best wishes,

Tomáš

Fri, Nov 09, 2018 ve 05:03:43PM +0100 Hans Hagen napsal(a):
# On 11/9/2018 4:24 PM, Jan U. Hasecke wrote:
# 
# >So context converts the SVG files to PDFs but does not change the colors
# >accordingly to CMYK.
# i don't know if inkscape has a switch for conversion
# 
# Hans
# 
# -----------------------------------------------------------------
#                                           Hans Hagen | PRAGMA ADE
#               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
#        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
# -----------------------------------------------------------------
# ___________________________________________________________________________________
# If your question is of interest to others as well, please add an entry to the Wiki!
# 
# maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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# ___________________________________________________________________________________

                                         Tomáš Hála
--------------------------------------------------------------------
Mendelova univerzita, Provozně ekonomická fakulta, ústav informatiky
Zemědělská 1, CZ-613 00 Brno,  tel. +420 545 13 22 28
--------------------------------------------------------------------
http://akela.mendelu.cz/~thala

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___________________________________________________________________________________

Re: Colormanagement

[luigi scarso]

[-- Attachment #1.1: Type: text/plain, Size: 1411 bytes --]

On Fri, Nov 9, 2018 at 4:24 PM Jan U. Hasecke <juh+ntg-context@mailbox.org>
wrote:

> Hi all,
>
> I defined some colors with \definecolor like this:
>
> \definecolor [myblue] [r=0.000, g=0.314, b=0.580, c=0.98,  m=0.67,
> y=0.03, k=0.12]
>
> \startnotmode[print]
> \setupcolors[cmyk=no,rgb=yes]
> \stopnotmode
>
> \startmode[print]
> \setupcolors[cmyk=yes,rgb=no]
> \setupbackend[
>         format=PDF/X-3:2003,
>    intent={ISO Coated v2 300\letterpercent\space (ECI)},
>    ]
> \stopmode
>
> When I use "context" or "context --mode=print" everything works as
> expected.
>
> But! I have SVG icons I want to use in the document. They contain the
> above defined rgb colors.
>
> When I use --mode=print I get different colors for the SVG icons.
>
> So context converts the SVG files to PDFs but does not change the colors
> accordingly to CMYK.
>
> What are my options? Do I miss something?
>
> 1. Let the designer produce icons in pdf with the given cmyk colors.
>
> 2. Don't use cmyk colors at all.
>
> In fact on my home printer the printed rgb colors look brighter than the
> cmyk colors. This might change in the print shop when they print with
> the right color profile, but it makes me nervous.
>

I think you should use the best colorspace (<something>rgb )
and let the print shop do its job -- of course this means that you have
signed  their sample (hard proof) of your project.


Hraban ?

-- 
luigi

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[-- Attachment #2: Type: text/plain, Size: 492 bytes --]

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___________________________________________________________________________________

Re: Colormanagement

[Jan U. Hasecke]

Am 09.11.18 um 17:18 schrieb Tomas Hala:
> Hi, 
> 
> by default, really not.
> 
> At http://wiki.inkscape.org/wiki/index.php/Color_management
> and http://wiki.inkscape.org/wiki/index.php/ExportPDFCMYK
> there some instructions how to convert files to CMYK,
> or how to install some extension, respectively.
> But I have not test these ways yet.
> 

These Python scripts does not work here. :-(

But I could ask my designer to convert the RGB-SVG into CMYK-PDF.

juh
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___________________________________________________________________________________

Re: Colormanagement

[Jan U. Hasecke]

Am 09.11.18 um 17:20 schrieb luigi scarso:
> I think you should use the best colorspace (<something>rgb )
> and let the print shop do its job -- of course this means that you have
> signed  their sample (hard proof) of your project.
> 

I really tend to do this. I am currently exploring the color management
system of ConTeXt together with a friend you is working as a color
manager in print industry.

And my first try was a failure. The cmyk values in the resulting pdf
file (with color profile) differs from the values we calculated (using
the same color profile in Gimp).

But we have to investigate  a bit further, so don't panic. Maybe I the
fault was mine.

Is there a test case tex file we could use to test the color management?

juh
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Re: Colormanagement

[Hans Hagen]

On 11/10/2018 2:34 PM, Jan U. Hasecke wrote:
> Am 09.11.18 um 17:20 schrieb luigi scarso:
>> I think you should use the best colorspace (<something>rgb )
>> and let the print shop do its job -- of course this means that you have
>> signed  their sample (hard proof) of your project.
>>
> 
> I really tend to do this. I am currently exploring the color management
> system of ConTeXt together with a friend you is working as a color
> manager in print industry.
> 
> And my first try was a failure. The cmyk values in the resulting pdf
> file (with color profile) differs from the values we calculated (using
> the same color profile in Gimp).
> 
> But we have to investigate  a bit further, so don't panic. Maybe I the
> fault was mine.
> 
> Is there a test case tex file we could use to test the color management?
there is no real 1-1 translation from rgb-cmyk .. in many programs that 
do that there is some additional magic (i remember that photoshop also 
applied the paper properties and that there was no roundtrip)

this is where color profiles come in

even viewers (like acrobat) can apply some magic so that the colors come 
out different from what you expect

try this on screen and in print:

\startMPpage

     path p ; p := fullcircle scaled 1cm ;

     fill p shifted (0cm,1cm) withcolor (1,1,0) ;
     fill p shifted (1cm,1cm) withcolor (0,0,1,0) ;
     fill p shifted (0cm,0cm) withcolor (1/2,1/2,0) ;
     fill p shifted (1cm,0cm) withcolor (0,0,1/2,0) ;

\stopMPpage


Hans


-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
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___________________________________________________________________________________

Issues with RGB to CMYK conversion with color profiles (was: Colormanagement)

[Jan U. Hasecke]

Hi all,

with the following file I tested the color conversion of context.

I get the same CMYK-values in the output pdf file using different color
profiles. A friend of mine can test the color values of PDF with a
special software.

My guess: the profiles are not used during pdf generation.
You can test this by commenting/uncommenting the other profile.

I created the files with

context --mode=print example.tex

My context version is
mtx-context     | ConTeXt Process Management 1.02
mtx-context     | current version: 2018.08.30 18:41


Is this the correct way of producing cmyk-pdfs?

I am missing the declaration of the RGB color profile. When doing color
management in Scribus I define two profiles: one for RGB and one for
CMYK. AFAIK you need both to convert rgb to cmyk.

Any hints?
juh

--- example.tex ---

\definecolor  [hs-logoblau]   [r=0.000, g=0.314, b=0.580]
\definecolor  [hs-dunkelblau] [r=0.258, g=0.474, b=0.737]
\definecolor  [hs-hellblau]   [r=0.6, g=0.737, b=0.858]
\definecolor  [hs-orange]     [r=0.866, g=0.286, b=0.003]

\startnotmode[print]
\setupcolors[cmyk=no,rgb=yes]
\stopnotmode

\startmode[print]
\setupcolors[cmyk=yes,rgb=no]
\setupbackend[
	format=PDF/X-1a:2003,
%   intent={ISO Coated v2 300\letterpercent\space (ECI)},
   intent={SWOP2006_Coated3v2.icc},
   ]
\stopmode

\setuppapersize [A4] [A4]

\starttext



\blackrule[width=3cm,height=1cm,depth=0pt,color=hs-orange] HS Orange
r=0.866, g=0.286, b=0.003
\blank

\blackrule[width=3cm,height=1cm,depth=0pt,color=hs-logoblau] HS Logoblau
r=0.000, g=0.314, b=0.580
\blank

\blackrule[width=3cm,height=1cm,depth=0pt,color=hs-dunkelblau] HS
Dunkelblau r=0.258, g=0.474, b=0.737
\blank

\blackrule[width=3cm,height=1cm,depth=0pt,color=hs-hellblau] HS Hellblau
r=0.6, g=0.737, b=0.858


\stoptext

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___________________________________________________________________________________

Re: Issues with RGB to CMYK conversion with color profiles

[Hans Hagen]

On 11/12/2018 9:02 AM, Jan U. Hasecke wrote:
> Hi all,
> 
> with the following file I tested the color conversion of context.
> 
> I get the same CMYK-values in the output pdf file using different color
> profiles. A friend of mine can test the color values of PDF with a
> special software.
> 
> My guess: the profiles are not used during pdf generation.
> You can test this by commenting/uncommenting the other profile.
> 
> I created the files with
> 
> context --mode=print example.tex
> 
> My context version is
> mtx-context     | ConTeXt Process Management 1.02
> mtx-context     | current version: 2018.08.30 18:41
> 
> 
> Is this the correct way of producing cmyk-pdfs?
> 
> I am missing the declaration of the RGB color profile. When doing color
> management in Scribus I define two profiles: one for RGB and one for
> CMYK. AFAIK you need both to convert rgb to cmyk.
> 
> Any hints?

it's probably better to define hs-dunkelblau etc in cmyk color space then

> juh
> 
> --- example.tex ---
> 
> \definecolor  [hs-logoblau]   [r=0.000, g=0.314, b=0.580]
> \definecolor  [hs-dunkelblau] [r=0.258, g=0.474, b=0.737]
> \definecolor  [hs-hellblau]   [r=0.6, g=0.737, b=0.858]
> \definecolor  [hs-orange]     [r=0.866, g=0.286, b=0.003]
> 
> \startnotmode[print]
> \setupcolors[cmyk=no,rgb=yes]
> \stopnotmode
> 
> \startmode[print]
> \setupcolors[cmyk=yes,rgb=no]
> \setupbackend[
> 	format=PDF/X-1a:2003,
> %   intent={ISO Coated v2 300\letterpercent\space (ECI)},
>     intent={SWOP2006_Coated3v2.icc},
>     ]
> \stopmode
> 
> \setuppapersize [A4] [A4]
> 
> \starttext
> 
> 
> 
> \blackrule[width=3cm,height=1cm,depth=0pt,color=hs-orange] HS Orange
> r=0.866, g=0.286, b=0.003
> \blank
> 
> \blackrule[width=3cm,height=1cm,depth=0pt,color=hs-logoblau] HS Logoblau
> r=0.000, g=0.314, b=0.580
> \blank
> 
> \blackrule[width=3cm,height=1cm,depth=0pt,color=hs-dunkelblau] HS
> Dunkelblau r=0.258, g=0.474, b=0.737
> \blank
> 
> \blackrule[width=3cm,height=1cm,depth=0pt,color=hs-hellblau] HS Hellblau
> r=0.6, g=0.737, b=0.858
> 
> 
> \stoptext
> 
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
> archive  : https://bitbucket.org/phg/context-mirror/commits/
> wiki     : http://contextgarden.net
> ___________________________________________________________________________________
> 


-- 

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
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Re: Issues with RGB to CMYK conversion with color profiles (was: Colormanagement)

[Jan U. Hasecke]

Hi all,

attached you find my colormanagement tests and I need your help to
understand and debug the situation.

I am testing together with a friend of mine, a professional
colormanager, who does not know ConTeXt.


There are several files in the archive:

The differences in the files are the color definition and the color
profile used.

- rgb-xxx.tex – colors are defined with RGB values only.

- rgb-cmyk-xxx.tex – colors are defined with RGB and CMYK values.

  The cmyk colors are derived from the rgb values using gimp and the
  color profiles sRGB/ISOCoated

- cmyk-xxx.tex – colors are defined with CMYK values only.

The xxx stand for two color profiles: iso-coated and swop.

What I see is this:

Colors in pdfs are the same no matter what color profile I choose.

With rgb values and rgb/cmyk values I get the same colors in pdf (the
wrong ones).

With cmyk values only I get other colors in pdf. Next week my friend
will test if these are the right ones.

I have many questions:

1. Is colormanagement working in ConTeXt at all?
2. Is my code correct?
3. Why do pdfs with different color profiles show the same colors?
4. Why does ConTeXt not take the cmyk colors from \definecolor when
there are rgb values as well?
5. Where can I define a coresponding rgb profile? In Scribus you have to
define two profiles (eg. sRGB and ISOCoated) to make colormanagement work.

TIA
juh
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Re: Issues with RGB to CMYK conversion with color profiles (was: Colormanagement)

[Jan U. Hasecke]

[-- Attachment #1: Type: text/plain, Size: 2072 bytes --]

I forgot the archive. :-(

Am 14.11.18 um 11:39 schrieb Jan U. Hasecke:
> Hi all,
> 
> attached you find my colormanagement tests and I need your help to
> understand and debug the situation.
> 
> I am testing together with a friend of mine, a professional
> colormanager, who does not know ConTeXt.
> 
> 
> There are several files in the archive:
> 
> The differences in the files are the color definition and the color
> profile used.
> 
> - rgb-xxx.tex – colors are defined with RGB values only.
> 
> - rgb-cmyk-xxx.tex – colors are defined with RGB and CMYK values.
> 
>   The cmyk colors are derived from the rgb values using gimp and the
>   color profiles sRGB/ISOCoated
> 
> - cmyk-xxx.tex – colors are defined with CMYK values only.
> 
> The xxx stand for two color profiles: iso-coated and swop.
> 
> What I see is this:
> 
> Colors in pdfs are the same no matter what color profile I choose.
> 
> With rgb values and rgb/cmyk values I get the same colors in pdf (the
> wrong ones).
> 
> With cmyk values only I get other colors in pdf. Next week my friend
> will test if these are the right ones.
> 
> I have many questions:
> 
> 1. Is colormanagement working in ConTeXt at all?
> 2. Is my code correct?
> 3. Why do pdfs with different color profiles show the same colors?
> 4. Why does ConTeXt not take the cmyk colors from \definecolor when
> there are rgb values as well?
> 5. Where can I define a coresponding rgb profile? In Scribus you have to
> define two profiles (eg. sRGB and ISOCoated) to make colormanagement work.
> 
> TIA
> juh
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
> archive  : https://bitbucket.org/phg/context-mirror/commits/
> wiki     : http://contextgarden.net
> ___________________________________________________________________________________
> 


[-- Attachment #2: farbmanagement.zip --]
[-- Type: application/zip, Size: 69827 bytes --]

[-- Attachment #3: Type: text/plain, Size: 492 bytes --]

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___________________________________________________________________________________

Re: Issues with RGB to CMYK conversion with color profiles (was: Colormanagement)

[Peter Rolf]

Hi Jan,

I donno if things have changed (ConTeXt is a fast moving target), so
take my answers with a grain of salt.

(1)
AFAIK there is no ACTIVE color management in ConTeXt in the sense that
there is an automatic color conversion from one profiled(!) colorspace
into another profiled color space. This means that all given colors
(objects) have to be in the correct (profiled) color space already!

Objects with embedded color profiles (e.g. a PDF bitmap graphic with icc
profile) will use those. Objects without a profile will use the
corresponding "default" color space profiles. These default color space
profiles can be defined via "profile" in \setupbackend.
This way every color in the PDF is defined properly.


(2)

I think so. Can't test, because my Windows 10 is beyond repair after
three "upgrades" and Acrobat is not working properly anymore.

(3)

Judging from the size of the final PDF, the icc profile is not embedded.
The profiles have to be installed in "the right place" (this includes
ConTeXt but also the PDF viewer software).

See "ICC profiles" section at

https://wiki.contextgarden.net/PDFX


(5) see (1) and (3)



Hope this helps,


Peter


Am 2018-11-14 um 11:39 schrieb Jan U. Hasecke:
> Hi all,
> 
> attached you find my colormanagement tests and I need your help to
> understand and debug the situation.
> 
> I am testing together with a friend of mine, a professional
> colormanager, who does not know ConTeXt.
> 
> 
> There are several files in the archive:
> 
> The differences in the files are the color definition and the color
> profile used.
> 
> - rgb-xxx.tex – colors are defined with RGB values only.
> 
> - rgb-cmyk-xxx.tex – colors are defined with RGB and CMYK values.
> 
>   The cmyk colors are derived from the rgb values using gimp and the
>   color profiles sRGB/ISOCoated
> 
> - cmyk-xxx.tex – colors are defined with CMYK values only.
> 
> The xxx stand for two color profiles: iso-coated and swop.
> 
> What I see is this:
> 
> Colors in pdfs are the same no matter what color profile I choose.
> 
> With rgb values and rgb/cmyk values I get the same colors in pdf (the
> wrong ones).
> 
> With cmyk values only I get other colors in pdf. Next week my friend
> will test if these are the right ones.
> 
> I have many questions:
> 
> 1. Is colormanagement working in ConTeXt at all?
> 2. Is my code correct?
> 3. Why do pdfs with different color profiles show the same colors?
> 4. Why does ConTeXt not take the cmyk colors from \definecolor when
> there are rgb values as well?
> 5. Where can I define a coresponding rgb profile? In Scribus you have to
> define two profiles (eg. sRGB and ISOCoated) to make colormanagement work.
> 
> TIA
> juh
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
> archive  : https://bitbucket.org/phg/context-mirror/commits/
> wiki     : http://contextgarden.net
> ___________________________________________________________________________________
> 

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Re: Issues with RGB to CMYK conversion with color profiles (was: Colormanagement)

[Jan U. Hasecke]

Thanks a lot, Peter.

Am 14.11.18 um 14:58 schrieb Peter Rolf:
> Hi Jan,
> 
> I donno if things have changed (ConTeXt is a fast moving target), so
> take my answers with a grain of salt.
> 
> (1)
> AFAIK there is no ACTIVE color management in ConTeXt in the sense that
> there is an automatic color conversion from one profiled(!) colorspace
> into another profiled color space. This means that all given colors
> (objects) have to be in the correct (profiled) color space already!
> 
> Objects with embedded color profiles (e.g. a PDF bitmap graphic with icc
> profile) will use those. Objects without a profile will use the
> corresponding "default" color space profiles. These default color space
> profiles can be defined via "profile" in \setupbackend.
> This way every color in the PDF is defined properly.

This would clarify some of the issues.

When I define rgb colors AND use not-print-modus I get the right rgb
colors in the pdf.

When I define cmyk colors AND use print modus I get colors that might be
correct (tested next week)

But obviously it is not possible to define both color spaces in
\definecolor because I don't get the same colors in the pdf as with the
cmyk-only defined file.

Maybe I misunderstood this, I've got a hint here, that I could define
rgb and cmyk in the same \definecolor and choose the right color space
in \setupcolors.

The correct method of defining rgb AND cmyk in the same file would be to
put the definecolor command inside a startstopmode-environment.

Can someone confirm this?

> 
> (2)
> 
> I think so. Can't test, because my Windows 10 is beyond repair after
> three "upgrades" and Acrobat is not working properly anymore.
> 
> (3)
> 
> Judging from the size of the final PDF, the icc profile is not embedded.
> The profiles have to be installed in "the right place" (this includes
> ConTeXt but also the PDF viewer software).
> 
> See "ICC profiles" section at
> 
> https://wiki.contextgarden.net/PDFX
> 

With --mode=print (which uses the color profiles) the pdf get bigger.
>10.000 compared to 8.000 without the mode. So I would guess that they
are included.

I hope I get this sorted out, because I want to print a series of
folders and other print products with ConTeXt in the near future.

juh

> (5) see (1) and (3)
> 
> 
> 
> Hope this helps,
> 
> 
> Peter
> 
> 
> Am 2018-11-14 um 11:39 schrieb Jan U. Hasecke:
>> Hi all,
>>
>> attached you find my colormanagement tests and I need your help to
>> understand and debug the situation.
>>
>> I am testing together with a friend of mine, a professional
>> colormanager, who does not know ConTeXt.
>>
>>
>> There are several files in the archive:
>>
>> The differences in the files are the color definition and the color
>> profile used.
>>
>> - rgb-xxx.tex – colors are defined with RGB values only.
>>
>> - rgb-cmyk-xxx.tex – colors are defined with RGB and CMYK values.
>>
>>   The cmyk colors are derived from the rgb values using gimp and the
>>   color profiles sRGB/ISOCoated
>>
>> - cmyk-xxx.tex – colors are defined with CMYK values only.
>>
>> The xxx stand for two color profiles: iso-coated and swop.
>>
>> What I see is this:
>>
>> Colors in pdfs are the same no matter what color profile I choose.
>>
>> With rgb values and rgb/cmyk values I get the same colors in pdf (the
>> wrong ones).
>>
>> With cmyk values only I get other colors in pdf. Next week my friend
>> will test if these are the right ones.
>>
>> I have many questions:
>>
>> 1. Is colormanagement working in ConTeXt at all?
>> 2. Is my code correct?
>> 3. Why do pdfs with different color profiles show the same colors?
>> 4. Why does ConTeXt not take the cmyk colors from \definecolor when
>> there are rgb values as well?
>> 5. Where can I define a coresponding rgb profile? In Scribus you have to
>> define two profiles (eg. sRGB and ISOCoated) to make colormanagement work.
>>
>> TIA
>> juh
>> ___________________________________________________________________________________
>> If your question is of interest to others as well, please add an entry to the Wiki!
>>
>> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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>> wiki     : http://contextgarden.net
>> ___________________________________________________________________________________
>>
> 
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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Re: Issues with RGB to CMYK conversion with color profiles (was: Colormanagement)

[Peter Rolf]

Am 2018-11-14 um 15:36 schrieb Jan U. Hasecke:
> Thanks a lot, Peter.
> 
> Am 14.11.18 um 14:58 schrieb Peter Rolf:
>> Hi Jan,
>>
>> I donno if things have changed (ConTeXt is a fast moving target), so
>> take my answers with a grain of salt.
>>
>> (1)
>> AFAIK there is no ACTIVE color management in ConTeXt in the sense that
>> there is an automatic color conversion from one profiled(!) colorspace
>> into another profiled color space. This means that all given colors
>> (objects) have to be in the correct (profiled) color space already!
>>
>> Objects with embedded color profiles (e.g. a PDF bitmap graphic with icc
>> profile) will use those. Objects without a profile will use the
>> corresponding "default" color space profiles. These default color space
>> profiles can be defined via "profile" in \setupbackend.
>> This way every color in the PDF is defined properly.
> 
> This would clarify some of the issues.
> 
> When I define rgb colors AND use not-print-modus I get the right rgb
> colors in the pdf.
> 
> When I define cmyk colors AND use print modus I get colors that might be
> correct (tested next week)
> 
> But obviously it is not possible to define both color spaces in
> \definecolor because I don't get the same colors in the pdf as with the
> cmyk-only defined file.
> 
> Maybe I misunderstood this, I've got a hint here, that I could define
> rgb and cmyk in the same \definecolor and choose the right color space
> in \setupcolors.
> 
> The correct method of defining rgb AND cmyk in the same file would be to
> put the definecolor command inside a startstopmode-environment.
> 
> Can someone confirm this?
>

Should work (the other part is invisible for ConTeXt).


>>
>> (2)
>>
>> I think so. Can't test, because my Windows 10 is beyond repair after
>> three "upgrades" and Acrobat is not working properly anymore.
>>
>> (3)
>>
>> Judging from the size of the final PDF, the icc profile is not embedded.
>> The profiles have to be installed in "the right place" (this includes
>> ConTeXt but also the PDF viewer software).
>>
>> See "ICC profiles" section at
>>
>> https://wiki.contextgarden.net/PDFX
>>
> 
> With --mode=print (which uses the color profiles) the pdf get bigger.
>> 10.000 compared to 8.000 without the mode. So I would guess that they
> are included.
>


Mh, the file size of "ISOcoated_v2_300_eci.icc" is around 1.7MB. I
highly doubt that ConTeXt can compress it into a 10KB PDF.

But I'm not so sure if PDF/X-3 needs embedding (there was an exception).
Never used it (only PDF/X-4p) and I can't remember the specifications
(all those stuff was added over 8 years ago).

I just assume you have installed the icc profiles properly (needs a
manual installation!) :D


> I hope I get this sorted out, because I want to print a series of
> folders and other print products with ConTeXt in the near future.
> 
> juh
> 
>> (5) see (1) and (3)
>>
>>
>>
>> Hope this helps,
>>
>>
>> Peter
>>
>>
>> Am 2018-11-14 um 11:39 schrieb Jan U. Hasecke:
>>> Hi all,
>>>
>>> attached you find my colormanagement tests and I need your help to
>>> understand and debug the situation.
>>>
>>> I am testing together with a friend of mine, a professional
>>> colormanager, who does not know ConTeXt.
>>>
>>>
>>> There are several files in the archive:
>>>
>>> The differences in the files are the color definition and the color
>>> profile used.
>>>
>>> - rgb-xxx.tex – colors are defined with RGB values only.
>>>
>>> - rgb-cmyk-xxx.tex – colors are defined with RGB and CMYK values.
>>>
>>>   The cmyk colors are derived from the rgb values using gimp and the
>>>   color profiles sRGB/ISOCoated
>>>
>>> - cmyk-xxx.tex – colors are defined with CMYK values only.
>>>
>>> The xxx stand for two color profiles: iso-coated and swop.
>>>
>>> What I see is this:
>>>
>>> Colors in pdfs are the same no matter what color profile I choose.
>>>
>>> With rgb values and rgb/cmyk values I get the same colors in pdf (the
>>> wrong ones).
>>>
>>> With cmyk values only I get other colors in pdf. Next week my friend
>>> will test if these are the right ones.
>>>
>>> I have many questions:
>>>
>>> 1. Is colormanagement working in ConTeXt at all?
>>> 2. Is my code correct?
>>> 3. Why do pdfs with different color profiles show the same colors?
>>> 4. Why does ConTeXt not take the cmyk colors from \definecolor when
>>> there are rgb values as well?
>>> 5. Where can I define a coresponding rgb profile? In Scribus you have to
>>> define two profiles (eg. sRGB and ISOCoated) to make colormanagement work.
>>>
>>> TIA
>>> juh
>>> ___________________________________________________________________________________
>>> If your question is of interest to others as well, please add an entry to the Wiki!
>>>
>>> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
>>> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
>>> archive  : https://bitbucket.org/phg/context-mirror/commits/
>>> wiki     : http://contextgarden.net
>>> ___________________________________________________________________________________
>>>
>>
>> ___________________________________________________________________________________
>> If your question is of interest to others as well, please add an entry to the Wiki!
>>
>> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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>> archive  : https://bitbucket.org/phg/context-mirror/commits/
>> wiki     : http://contextgarden.net
>> ___________________________________________________________________________________
>>
> 
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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> 

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Re: Issues with RGB to CMYK conversion with color profiles (was: Colormanagement)

[Jan U. Hasecke]

Am 14.11.18 um 16:04 schrieb Peter Rolf:
> Mh, the file size of "ISOcoated_v2_300_eci.icc" is around 1.7MB. I
> highly doubt that ConTeXt can compress it into a 10KB PDF.
> 
> But I'm not so sure if PDF/X-3 needs embedding (there was an exception).
> Never used it (only PDF/X-4p) and I can't remember the specifications
> (all those stuff was added over 8 years ago).
> 
> I just assume you have installed the icc profiles properly (needs a
> manual installation!) :D

There are some profiles in the context installation.

At least something was found:

backend         > profiles > profile specification
'ISOcoated_v2_300_eci.icc' loaded from
'/home/juh/context/tex/texmf-context/colors/icc/context/colorprofiles.xml'
backend         > profiles > omitting reference to profile for intent
'ISO Coated v2 300% (ECI)'

But, yes the size is too small to have the whole profile incorporated.

juh
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Re: Issues with RGB to CMYK conversion with color profiles

[Wolfgang Schuster]

Jan U. Hasecke schrieb am 14.11.18 um 11:39:
> Hi all,
>
> attached you find my colormanagement tests and I need your help to
> understand and debug the situation.
>
> I am testing together with a friend of mine, a professional
> colormanager, who does not know ConTeXt.

Even without a color profile the results from the normal conversion of 
colors from cmyk to rgb
can result in differences between ConTeXt and Gimp because both use 
different formulas.

This is the formula from ConTeXt (attr-col.lua)

r = 1.0 - math.min(1.0,c+k)
g = 1.0 - math.min(1.0,m+k)
b = 1.0 - math.min(1.0,y+k)

and this is the one from Gimp 
(https://gitlab.gnome.org/GNOME/gimp/blob/master/libgimpcolor/gimpcolorspace.c)

r = 1.0 - math.min(1.0,c*(1.0-k)+k)
g = 1.0 - math.min(1.0,m*(1.0-k)+k)
b = 1.0 - math.min(1.0,y*(1.0-k)+k)

Wolfgang

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Re: Issues with RGB to CMYK conversion with color profiles

[Hans Hagen]

On 11/14/2018 4:51 PM, Wolfgang Schuster wrote:
> Jan U. Hasecke schrieb am 14.11.18 um 11:39:
>> Hi all,
>>
>> attached you find my colormanagement tests and I need your help to
>> understand and debug the situation.
>>
>> I am testing together with a friend of mine, a professional
>> colormanager, who does not know ConTeXt.
> 
> Even without a color profile the results from the normal conversion of 
> colors from cmyk to rgb
> can result in differences between ConTeXt and Gimp because both use 
> different formulas.
> 
> This is the formula from ConTeXt (attr-col.lua)
> 
> r = 1.0 - math.min(1.0,c+k)
> g = 1.0 - math.min(1.0,m+k)
> b = 1.0 - math.min(1.0,y+k)
> 
> and this is the one from Gimp 
> (https://gitlab.gnome.org/GNOME/gimp/blob/master/libgimpcolor/gimpcolorspace.c) 
> 
> 
> r = 1.0 - math.min(1.0,c*(1.0-k)+k)
> g = 1.0 - math.min(1.0,m*(1.0-k)+k)
> b = 1.0 - math.min(1.0,y*(1.0-k)+k)
Are there more variants? Do we need to support variants?

Hans


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Re: Issues with RGB to CMYK conversion with color profiles

[Henning Hraban Ramm]

Am 2018-11-18 um 19:26 schrieb Hans Hagen <j.hagen@xs4all.nl>:

> On 11/14/2018 4:51 PM, Wolfgang Schuster wrote:
>> Jan U. Hasecke schrieb am 14.11.18 um 11:39:
>>> Hi all,
>>> 
>>> attached you find my colormanagement tests and I need your help to
>>> understand and debug the situation.
>>> 
>>> I am testing together with a friend of mine, a professional
>>> colormanager, who does not know ConTeXt.
>> Even without a color profile the results from the normal conversion of colors from cmyk to rgb
>> can result in differences between ConTeXt and Gimp because both use different formulas.
>> This is the formula from ConTeXt (attr-col.lua)
>> r = 1.0 - math.min(1.0,c+k)
>> g = 1.0 - math.min(1.0,m+k)
>> b = 1.0 - math.min(1.0,y+k)
>> and this is the one from Gimp (https://gitlab.gnome.org/GNOME/gimp/blob/master/libgimpcolor/gimpcolorspace.c) r = 1.0 - math.min(1.0,c*(1.0-k)+k)
>> g = 1.0 - math.min(1.0,m*(1.0-k)+k)
>> b = 1.0 - math.min(1.0,y*(1.0-k)+k)
> Are there more variants? Do we need to support variants?

Oh my, color separation is a science of its own, but not an exact science...

Any really usable color conversion algorithm uses color profiles.

It would make sense to outsource color calculations to a color management library like LittleCMS.


Greetlings, Hraban
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Re: Issues with RGB to CMYK conversion with color profiles

[luigi scarso]

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On Mon, Nov 19, 2018 at 10:57 AM Henning Hraban Ramm <texml@fiee.net> wrote:

>
>
It would make sense to outsource color calculations to a color management
> library like LittleCMS.
>
> yes.
Perhaps this is still useful
 https://www.tug.org/TUGboat/tb31-3/tb99scarso.pdf

-- 
luigi

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Re: Issues with RGB to CMYK conversion with color profiles

[Jan U. Hasecke]

Am 19.11.18 um 11:14 schrieb luigi scarso:

> Perhaps this is still useful 
>  https://www.tug.org/TUGboat/tb31-3/tb99scarso.pdf

Thanks a lot for the hint.

I don't understand the equations but at least I found transicc to
calculate color conversions.

What precision is useful in the wild?

I now use three digits after the decimal point, eg.:

\definecolor [hs-logoblau] [c=0.976, m=0.665, y=0.028, k=0.116]

juh
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Re: Issues with RGB to CMYK conversion with color profiles

[luigi scarso]

[-- Attachment #1.1: Type: text/plain, Size: 1112 bytes --]

On Wed, Nov 21, 2018 at 3:02 PM Jan U. Hasecke <juh+ntg-context@mailbox.org>
wrote:

> Am 19.11.18 um 11:14 schrieb luigi scarso:
>
> > Perhaps this is still useful
> >  https://www.tug.org/TUGboat/tb31-3/tb99scarso.pdf
>
> Thanks a lot for the hint.
>
> I don't understand the equations but at least I found transicc to
> calculate color conversions.
>
> What precision is useful in the wild?
>
> I now use three digits after the decimal point, eg.:
>
> \definecolor [hs-logoblau] [c=0.976, m=0.665, y=0.028, k=0.116]
>
> It's safe to specify a color as 8bit per channel rgb, or in percent. i.e.
see for example
https://en.wikipedia.org/wiki/List_of_colors:_A%E2%80%93F
(more on  https://en.wikipedia.org/wiki/Lists_of_colors )

16bit per channel rgb are also possible, but old RIP can have problems
 (for example
https://www.pantone.com/color-finder/#/pick?pantoneBook=pantoneSolidCoatedV3M2
shows rgb 8bit per channel  and CMYK 0 to 100)

Btw: be careful of the  checker shadow illusion
 https://en.wikipedia.org/wiki/Optical_illusion
colors not always look as they are expressed  in numeric form.

-- 
luigi

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