color question

color question

[jbf]

I have a very basic question about color use that someone will be able 
to answer easily. The background to the question is that (i) I am 
completely new to this scene of commercially[offset] print-ready 
material as distinct from what is required on screen (ii) I am using Mk 
IV (iii) I need spot colors set up for cmyk, and for now I need shades 
between black and white (e.g. light gray) for a simple design feature.

My question is this: is the use of color keywords sufficient? Or in 
other words, have predefined color names like lighgray already been 
defined in, say cmyk terms behind the scenes, or must I instead 
\definecolor[lightgray][c=10,m=7,y=5,k=0],   (or perhaps 
\definespotcolor with those dimensions, or do I need both)?

Julian

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Re: color question

[Henning Hraban Ramm]

> Am 24.08.2020 um 01:15 schrieb jbf <roma83537@gmail.com>:
> 
> I have a very basic question about color use that someone will be able to answer easily. The background to the question is that (i) I am completely new to this scene of commercially[offset] print-ready material as distinct from what is required on screen (ii) I am using Mk IV (iii) I need spot colors set up for cmyk, and for now I need shades between black and white (e.g. light gray) for a simple design feature.
> 
> My question is this: is the use of color keywords sufficient? Or in other words, have predefined color names like lighgray already been defined in, say cmyk terms behind the scenes, or must I instead \definecolor[lightgray][c=10,m=7,y=5,k=0],   (or perhaps \definespotcolor with those dimensions, or do I need both)?

First: Color parts use decimal numbers from 0 to 1.

Even if some color names are predefined, you should define your grays yourself – either as shades of black only or maybe with a bit of cyan. Grays in more (process) colors are unstable and might get a tint (color cast) you don’t want. (Of course you could use other colors than cyan for some tinting, depending on your work.)

E.g. I often \definecolor[deepblack][c=.3,k=1] for black areas; the cyan portion evens out some irregularities in print.
Because I don’t trust ConTeXt’s (or my) color setup, I also \definecolor[cmykblack][k=1] to avoid “RGB black”. (But \setupcolor[cmyk=yes,rgb=no,overprint=yes] should handle that already.)

If you want to use grays as spot colors (e.g. Pantone) you must define them as such – but usually you don’t want (to pay for) more than one spot color. Spot gray makes sense if you have big areas of that color, since 100% spot color looks better than any percent rastered black.

See also:
https://wiki.contextgarden.net/Color
https://wiki.contextgarden.net/Spot_Colors


Hraban (printing engineer)

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Re: color question

[Alan Bowen]

On Oct 10, 2006, at 12:30 PM, gnwiii@gmail.com wrote:

> On 10/10/06, Alan Bowen <acbowen@princeton.edu> wrote:
>> If this is OT, my apologies to all.
>>
>> I am currently using ConTEXt to produce PDFs with a colored
>> background which I specify using R G B settings. Unfortunately, this
>> background does not look the same when others open the files on their
>> computers. Is there anything I can do at my end to correct this?
>
> There are well-known differences between various computer brands, and
> individual PC's generally vary widely. If you need really good
> agreement, then all the systems need to be viewed under similar light
> conditions and calibrated (e.g., using a colorimeter, or at least the
> GretagMacbeth ColorChecker, a printed chart) and you want to generate
> PDF's with a specific colorspace (not just deviceRGB).  For most
> purposes, it seems to work to use a rough "sRGB" setting where you
> adjust the monitor (brightness, contrast) to approximate gamma=2.2.
> Check this with:
> <http://www.normankoren.com/ 
> makingfineprints1A.html#Monitor_test_pattern>.
>
> Many LCD's and worn-out CRT's like the ancient NCD on my desk will
> fail even this simple test.
>
> -- 
> George N. White III <aa056@chebucto.ns.ca>
> Head of St. Margarets Bay, Nova Scotia


Henning and George—

Thanks for the replies. I had suspected that I was at the start of a  
search for yet another Holy Grail. Still, I will look into this sRGB  
(which is new to me), but first I had better see if I can calibrate  
my own monitor properly. (It failed the Monitor test.)

Alan

Re: color question

[Henning Hraban Ramm]

Am 2006-10-10 um 13:52 schrieb Alan Bowen:

> I am currently using ConTEXt to produce PDFs with a colored
> background which I specify using R G B settings. Unfortunately, this
> background does not look the same when others open the files on their
> computers. Is there anything I can do at my end to correct this?

Color almost never looks the same on some other screen - you can't  
force everyone to calibrate theirs and use proper color management  
settings...


Greetlings from Lake Constance!
Hraban
---
http://www.fiee.net/texnique/
http://contextgarden.net
http://www.cacert.org (I'm an assurer)

Re: color question

[gnwiii]

On 10/10/06, Alan Bowen <acbowen@princeton.edu> wrote:
> If this is OT, my apologies to all.
>
> I am currently using ConTEXt to produce PDFs with a colored
> background which I specify using R G B settings. Unfortunately, this
> background does not look the same when others open the files on their
> computers. Is there anything I can do at my end to correct this?

There are well-known differences between various computer brands, and
individual PC's generally vary widely. If you need really good
agreement, then all the systems need to be viewed under similar light
conditions and calibrated (e.g., using a colorimeter, or at least the
GretagMacbeth ColorChecker, a printed chart) and you want to generate
PDF's with a specific colorspace (not just deviceRGB).  For most
purposes, it seems to work to use a rough "sRGB" setting where you
adjust the monitor (brightness, contrast) to approximate gamma=2.2.
Check this with:
<http://www.normankoren.com/makingfineprints1A.html#Monitor_test_pattern>.

Many LCD's and worn-out CRT's like the ancient NCD on my desk will
fail even this simple test.

-- 
George N. White III <aa056@chebucto.ns.ca>
Head of St. Margarets Bay, Nova Scotia

color question

[Alan Bowen]

If this is OT, my apologies to all.

I am currently using ConTEXt to produce PDFs with a colored  
background which I specify using R G B settings. Unfortunately, this  
background does not look the same when others open the files on their  
computers. Is there anything I can do at my end to correct this?

Alan

Re: color question

[Hans Hagen]

At 06:03 AM 5/23/2002 +0200, you wrote:

>When I try
>
>\startcolor[blue]
>\rightaligned{\framed[background=screen]{historic background}}
>\stopcolor

the problem seems to be related to screens,

background=color,backgroundcolor=red

works ok, (screens are normally only used in (page) backgrounds and there 
they don't nest, and since they don't form a color stack (just raw gray 
scale switches) this goes wrong inside color, maybe i should implement a 
stack)

Hans

================ can go into cont-new.tex ================

\def\setrastercolor#1%
   {\edef\@@cl@@s{#1}%
    \ifx\@@cl@@s\empty
      \let\@@rsraster
    \fi
    \setevalue{\??cr\??rs}{\colorSpattern}}

\def\localstartraster[#1]%
   {\bgroup\setrastercolor{#1}\localstartcolor[\??rs]}

\def\localstopraster
   {\localstopcolor\egroup}

\def\startraster[#1]%
   {\bgroup\setrastercolor{#1}\startcolor[\??rs]}

\def\stopraster
   {\stopcolor\egroup}

This alternative is slower, but run on top of the color mechanism

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                                   Hans Hagen | PRAGMA ADE | pragma@wxs.nl
                       Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
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Re: color question

[Hans Hagen]

At 06:03 AM 5/23/2002 +0200, Denis B. Roegel wrote:

>When I try
>
>\startcolor[blue]
>\rightaligned{\framed[background=screen]{historic background}}
>\stopcolor
>
>I get no blue at all, even though I have
>
>\setupcolors[state=start]
>
>Is this what is supposed to happen?

no, this smells like a bug (actually an interference between catching a 
global doc color problem (we need to make sure that no lone color marks end 
up on empty pages, as well as forgroundcolors in framed texts),

i will look into it

Hans
-------------------------------------------------------------------------
                                   Hans Hagen | PRAGMA ADE | pragma@wxs.nl
                       Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
  tel: +31 (0)38 477 53 69 | fax: +31 (0)38 477 53 74 | www.pragma-ade.com
-------------------------------------------------------------------------
                        information: http://www.pragma-ade.com/roadmap.pdf
                     documentation: http://www.pragma-ade.com/showcase.pdf
-------------------------------------------------------------------------

color question

[Denis B. Roegel]

When I try

\startcolor[blue]
\rightaligned{\framed[background=screen]{historic background}}
\stopcolor

I get no blue at all, even though I have

\setupcolors[state=start]

Is this what is supposed to happen?

Thanks,

Denis

Re: Color question

[Hans Hagen]

David Arnold wrote:

> Suppose I want all text set with \starttyping...\stoptyping, as in
> 
>  \starttyping
> >> [x,y]=meshgrid(-2:.1:2);
> >> z=-3*y./(x.^2+y.^2+1);
> >> contour(x,y,z)
>  \stoptyping
> 
> to be red. What's the best way to go about it?

Wait till the next release. In the texexec/texutil manuals I posted a
few days ago, you can see this feature at work. 

Before I post it, I muts be sure that the color directives don't
interfere with spacing. Actually it's only 4 lines of code and a color
key in the setup macros. 

Hans

-----------------------------------------------------------------
                                          Hans Hagen | PRAGMA ADE
              Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
      tel: 038 477 53 69 | fax: 038 477 53 74 | www.pragma-ade.nl
-----------------------------------------------------------------

Color question

[David Arnold]

All,

Suppose I want all text set with \starttyping...\stoptyping, as in

 \starttyping
>> [x,y]=meshgrid(-2:.1:2);
>> z=-3*y./(x.^2+y.^2+1);
>> contour(x,y,z)
 \stoptyping

to be red. What's the best way to go about it?