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Screen and Printer Colour Matching

Why do I need Colour Matching ?

As more and more people use Colour monitors and introduce colour images
into their work a problem getting hardcopies is created. When a hardcopy
of an image on the screen is produced the colours have to be converted
from the Red, Green and Blue (RGB) colourspace to the Cyan, Magenta, Yellow
and Black (CMYK) colourspace. This conversion is usually done by the printer
itself, but does not take account of the different colours a printer and
screen can display. Since the conversion is not done correctly the images
produced on the colour printer differ greatly from the original image on the

Algorithms exist for doing a better conversion from RGB to CMYK, but they
usually need the user to be an expert in colour theory and spend a large
amount of time tweaking the images. Quite often the equipment needed to 
take the necessary measurements for these algorithms is expensive to hire/buy
and so people put up with inferior images.

What does the package do ?

This colour matching package gives a simple method of matching images on
monitors and printers. The user does not need to know anything about the
underlying algorithms, and does not need any specialist equipment. The
only equipment required is a Kodak Reflection Density Guide (Kodak
Publication Q-16) which can be found in most reprographics departments.

The package is made up of a number of programs each performing a specific
task in the colour matching process. In order to start the colour matching
process please read the following documents that accompany this package. The
documents can be found in the 'doc' directory once the package has been
unpacked. (see below)

ralcolour_match	- Provides an overview of the whole colour matching process.
ralcol_match	- Manual page for the program used in taking measurements.
16shades	- Manual page for the program used to calibrate the monitor.
midtone		- Manual page for the program used to take monitor measurements
charts		- Manual page for the printer test charts.
ralmatch	- Manual page for the command line version of the colour
		   matching program.
ralmatchx	- Manual page for the Motif version of the colour matching

Before attempting to use the colour matching package please read the above

How to unpack the Colour Matching package

Once the tar file has been retrieved you can unpack it as follows :-

First cd to where you want the colour matching package to be located and
then type the following.

% uncompress ralcol_match.tar.Z

% tar xvf ralcol_match.tar

This will create a number of files and directories taking up approximately
160 KBytes of disk space. Instructions on how to build the package can be
found in the INSTALL file.