[OS X TeX] White vs. Transparent?

V. Yu. Shavrukov vshavruk at science.uva.nl
Mon Apr 3 10:21:58 CEST 2006

On Apr 2, 2006, at 20:45, Peter Dyballa wrote:
> Am 02.04.2006 um 19:17 schrieb V. Yu. Shavrukov:
>> The way I see it, there are no such things as "colours in the  
>> graphics file" (as long as we are talking untagged rgb or cmyk  
>> data, as has been the case in this discussion).
> No, I wasn't talking about that.

Indeed you weren't.  I was.

> I was very simply assuming that the green I've chosen has 25% red,  
> 100% green, and 62.5% blue.

This phrase is meaningless.  It does not specify a colour unless and  
until you fix the physical meaning of "red", "25% thereof" etc.  It's  
like talking local coordinates on a manifold without specifying a chart.

> Now my display and my printer are asked to reproduce this correctly.

Accordingly, the issue of reproducing all that "correctly" is moot.

> In my view my wish is device independent. In my view it's OK when  
> these values are stored uncommented, without tags.

Again, there should be some mechanism for tying numerical data to  
colours.  There is no worldwide "default" for that.  One solution  
would be to tie the data to one of the "standard" profiles, like  
sRGB, ARGB etc.  Unfortunately, I am not aware of any way (short of  
using profile-tagged coloured fonts from InDesign) to do this with  
pdftex, so I'm looking for workarounds.  A workaround that insures  
that Mr. X's pdf viewer puts the same interpretation on untagged rgb  
as my pdf viewer (Preview/iTeXMac/TeXShop) does would be to tie the  
data to my viewer's interpretation of untagged rgb.  That  
interpretation is believed to be Generic RGB, and this is what I  
would like to embed in the pdf file as the profile to use for that  
rgb data that is not already tagged with a profile.

When I am viewing that pdf file, the rgb data is converted to my  
display's profile.  When Mr. X views the file, the data is converted  
to Mr. X's display's profile.  In this picture Generic RGB plays the  
role of the source profile, and my and Mr. X's display profiles the  
role of destination profiles.  The variable that I'm trying to fix is  
what Mr. X uses for source profile.

Let me point out that Mr. X can mean anybody, I don't personally know  
Mr. X, and have no access to nor interest in his display profile.

>> Why should my screen's profile be stored in the file? Who is  
>> interested in this?

I share your puzzlement at these questions.

> Apple's generic screen profiles are a fine service, from a company  
> that delivers the software and the hardware. Sun, IBM, and HP  
> probably deliver a similiar service. This is a situation I prefer  
> more than that with some BSD, Linux, or MS Windows on arbitrary  
> hardware -- what would that do with my profile?

I fail to see any difference between Apple and other manufacturers in  
this regard.  Basically any display vendor supplies an icc profile  
with their monitor that describes the display model.  Of course you  
can compare vendors on how accurate those profiles are and how large  
the individual variation between units is.  Apple is far from being  
the best on that score.

> And I still think that you need to know your printer paper's   
> profile, too.

If I had an individual printer in mind than yes that would be a good  
idea.  In this discussion I have been concerned with Mr. X's printer  
- I don't know who that is, what printer he uses or the paper he  
prints on.  The best I can do is ensure that Mr. X has solid starting  
data.  Largely everything I've said above about monitors applies to  

sincerely yours,
Volodya Shavrukov
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