[OS X TeX] Re: LaTeXiT & Keynote: color management when printing

Jens Noeckel noeckel at uoregon.edu
Wed Sep 26 21:04:26 CEST 2007

On Sep 26, 2007, at 11:51 AM, Adam M. Goldstein wrote:

> On Sep 26, 2007, at 12:54 PM, Luis Sequeira wrote:
>>> 	This question may be slightly afield for many folks on this list,
>>> but since in involves Macs and LaTeX, I hope the rest of you will
>>> indulge me:
>>> 	I am using a 3rd-party Keynote theme along with LaTeXiT for a  
>>> course
>>> I am teaching this semester.  The theme has a dark blue background
>>> with white text;  I use LaTeXiT to produce equations in the same  
>>> font
>>> and text color.  Of course, these equations are seen by Keynote as
>>> embedded PDFs.
>>> 	For student versions of the slides (with space to write notes), I
>>> generate PDFs of each lecture's notes using the Keynote print option
>>> "Don't print slide background or object fills" -- this, in
>>> combination with the ColorSync print option to use the "Grey Tone"
>>> Quartz filter, yields compact versions of the slides that print with
>>> black text on a white background.
>>> 	Except for the equations, that is -- these (naturally) are still
>>> white and thus rendered "invisible" in the PDFs of the slide  
>>> handouts
>>> that the students print prior to lecture.  I could go in and change
>>> each and every equation manually from a white to a black text color
>>> (thereby having to maintain two versions of each lecture
>>> presentation:  the white-on-blue lecture slides and the black-on-
>>> white handouts).  But I'm hoping for a better alternative.  (The
>>> slide-to-equation ratio is slightly over 2, but that still leaves 15
>>> - 30 equations per lecture to modify by hand.)
>>> 	I suspect that it should be possible to use CoreImage and/or Quartz
>>> filters to first "invert" the colors (if that is the right term) so
>>> that white text -> black text, dark blue background -> light-colored
>>> background, etc., then filter a second time to create a greyscale
>>> version of this transformed color scheme.  All via the print dialog,
>>> or maybe Automator.  Unfortunately, I have not been able to find a
>>> way to accomplish this objective (and I have neither skills in, nor
>>> access to, Photoshop or Illustrator, etc.).
>>> 	If a LaTeX-based presentation package can do all this, as well as
>>> manage data chart creation and complex slide transitions and dynamic
>>> graphics, then I would like to know about it.  However, I am not  
>>> in a
>>> position to switch away from Keynote this semester, so suggestions
>>> for a more direct solution would be greatly appreciated.
>>>                                          -- Mike
>> Both powerdot and (as has been said by another poster) beamer can  
>> handle this perfectly.
>> I use powerdot for my classes and usually keep two versions of the  
>> \documentclass line, such as
>> \documentclass[mode=present,paper=a4paper,display=slides]{powerdot}
>> %\documentclass[mode=handout,display=slidesnotes,nopagebreaks] 
>> {powerdot}
>> and I just comment/uncomment one and the other, as appropriate, to  
>> produce screen or handout versions. Works like a charm.
>> Luis Sequeira
> I use beamer in a similar manner, producing 4-up copies of the  
> slide show by commenting and uncommenting short segments in the  
> preamble, depending upon whether I am producing a version to show  
> in class or a version to be distributed as lecture notes. The  
> colors are altered as well as the number of slides per page.


That's definietly the best way to solve the original problem. Now  
that he's already started using Keynote, though, it should in  
principle be possible to just go through all the dropped LaTeXiT  
pictures and process them, ideally by extracting their LaTeX source  
and just modifying the foreground and/or background color information.

If you do "Show Package Contents" on a Keynote presentation, all the  
equations show up as pdf files starting with "droppedImage". So all  
one has to do is write a script that goes through these  
droppedImage*.pdf files one by one, and replaces them with a new  
version. Of course one should work on a copy of the presentation,  
because any post-processing will probably conflict with the LaTeXiT  
linkback functionality.

The easiest thing one could do, although it's not exactly what Mike  
wanted, is to add a dark background to each formula, without changing  
anything else. So the foreground of each equation  would still be  
white, but at least it would be visible in the printout. To do that,  
for each "droppedImage.pdf" file in the presentation bundle, you  
could create a temporary file "tfile.tex" with the content


Executing "pdflatex tfile" would create the tfile.pdf which has a  
background with RGB values I just chose at random above. This then  
has to replace the original droppedImage.pdf.

Repeating this for all LaTeXiT files, you end up with a Keynote  
presentation that has all the equations with a dark background. I  
just tried this myself, and interestingly I can still get the color- 
changed equations to open in LaTeXiT with Linkback. However, my added  
background color of course gets lost in this return trip to LaTeXiT.

Anyway, although not perfect, this is an easily scriptable partial  
solution to the problem, which doesn't require going back to the  
source of each equation. One could say it has the advantage of making  
the math stand out more.

Probably I could come up with a script if someone thinks this is a  
useful idea. One could obviously extend this to negate the whole  
picture with ImageMagick to get even closer to the original intent.


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