# A Light Colour Theme for Beamer Poster

(Yes it’s been a while. I’ve started working and adapting to the new pace!)

So quite a (long) while ago, I posted my sample beamer poster, while preparing for a conference poster. Now I’ve got another poster to present, and the previous colour schemes just did not go well with the logos. Hence I started tinkering around with the colours, and finally settled on this light, subtle palette:

.

The sample poster looks like these (shown together with the existing two other colour themes):

And here’s a thumbnail of the actual poster:

Source code of the sample files (including Beamer themes and colours) can be downloaded here.

# CMYK Output for Printing Prepress

This is the 6th and real last post in the bookdesign series. Previous posts in this series:

Happy Chinese New Year! Well traditionally CNY is celebrated up till the 15th day, so this isn’t a belated greeting. 😉

I thought my post on the front and back covers (+ISBN bar codes) was the last thing I wanted to document in the bookdesign series, but I just realised that I’d still yet to talk about producing a CMYK version if your printer is using a offset-printing process.

You can read about the CMYK colour model and how it it’s different from RGB. In a nutshell, RGB is for on-screen viewing and is more vibrant, CMYK is for commercial printing and seems more “dull”. Check with your printing service if they’re using (on-demand) laser printing or offset-printing to print your material; it may depend on the type of printing stock (i.e. the paper) you choose.

If laser printing is used, RGB is fine, and you can hand over your pdflatex-generated file over as it is. However if offset-printing is to be used, you’ll need to produce your PDF in CMYK colour model instead. Your printing service might be willing to do the conversion for you at their end; but I think it’s more efficient to do this yourself as you’ll have more control over the final PDF. It’ll also give you a more accurate idea of how your design will look in print, so you’ll have a chance of selecting your colours.

### Convert all graphics files to CMYK

Any graphic files that you include (via \includegraphics, for example) must be converted to CMYK. If you have imagemagick, the quick way is

convert image_RGB.jpg -colorspace CMYK image_CMYK.jpg

But I’ve been told that the resulting PDF, when loaded into other applications e.g. Illustrator, contains the “wrong” colours. For more accurate results, you’ll need to use colour profiles as discussed here.

### Invoke xcolor CMYK mode

By default, the xcolor package uses the RGB colour model. To invoke CMYK mode:

\usepackage[cmyk, …other options…]{xcolor}

And then there’s the issue of different kinds of black. If your design contains large areas of black, and particularly if it involves light-coloured text (e.g. white) on a black background, the RGB black directly converted to CMYK would have values of C: 100% M: 100% Y: 100% K: 100% (over-saturated rich black). You then run high risks of getting unwanted “shadows” if the four colours print out of registration, as shown in the sample on the right from this excellent article:

Now the cmyk mode of the xcolor package automatically redefines the colour black to C: 0% M: 0% Y: 0% K: 100%, i.e. flat or standard black. Flat black can look rather “washed-out”, so you might want to define a different shade of black, especially for large areas of black. Check with your printing service for further advice. E.g. our printer recommended to use a “cool black”  C: 30% M: 0% Y: 0% K: 100% for the covers of our Grid Computing Cluster book. Unfortunately I couldn’t figure out how to do it previously, but now I do:

\usepackage[cmyk, …other options…]{xcolor}

%% cmyk values have range [0,1]
\definecolor{CoolBlack}{cmyk}{.3,0,0,1}

%% In case you want to redefine the basic black
%% (0,0,0,1) across the board. Check with your
%% printer if this is advisable!!

\definecolor{black}{cmyk}{.4,.3,.3,1}

%% Force the new black into effect, because
%% xcolor issues \color{black} with the old
%% black before all its initialisations.

\color{black}

In other words, you should always liaise with your printing service concerning the technical specs. You’ll thank them for their expert advice, and you’ll learn a lot about graphics design and the printing process as well.

OK that’s it! That’s truly the last of the bookdesign series. I hope you’ve enjoyed it as much as I did.

# Using Colours in LaTeX

A brief departure from the bookdesign series, as some of my future posts within and outside the series will be dealing with the use of colours, so I might as well get it out of the way first. Summarily, we’ll take a look at how to use colours in LaTeX with the xcolor package. This will work with all outputs, i.e. .dvi, .ps and .pdf.

The most useful commands for applying colours made available by xcolor are:

• \color{color} (applies color to the text in the currrent group)
• \textcolor{color}{text} (applies color to the specified text only)
• \pagecolor{color} (colors the entire page to be color)
• \colorbox{color}{text} (creates a box containing the specified text, with color as the background)
• \fcolorbox{frame color}{bg color}{text} (same as above, but with a coloured border around the box)

See Section 2.6 of the xcolor manual for full list and more details of commands for colour application. Alternatively, if you’re using emacs, you can look it up with

The xcolor package has quite a collection of pre-defined colours; they are listed in Section 4 Colors by Name in the manual. Apart from the 19 “base” colours that are always available, you can also access more pre-defined colours via the dvipsnames, svgnames and x11names options. Here’s a quick example:

\documentclass[a6paper,12pt]{article}
\usepackage[x11names]{xcolor}

\begin{document}

% ‘LemonChiffon1’ from x11names
\pagecolor{LemonChiffon1}

% ‘magenta’ is a base colour
\textcolor{magenta}{Hello World!}

% are available via x11names