2 research outputs found
Computer mediated colour fidelity and communication
Developments in technology have meant that computercontrolled
imaging devices are becoming more powerful and more
affordable. Despite their increasing prevalence, computer-aided
design and desktop publishing software has failed to keep pace, leading
to disappointing colour reproduction across different devices.
Although there has been a recent drive to incorporate colour management
functionality into modern computer systems, in general this
is limited in scope and fails to properly consider the way in which
colours are perceived. Furthermore, differences in viewing conditions
or representation severely impede the communication of colour
between groups of users.
The approach proposed here is to provide WYSIWYG colour
across a range of imaging devices through a combination of existing
device characterisation and colour appearance modeling techniques.
In addition, to further facilitate colour communication, various common
colour notation systems are defined by a series of mathematical
mappings. This enables both the implementation of computer-based
colour atlases (which have a number of practical advantages over
physical specifiers) and also the interrelation of colour represented in
hitherto incompatible notations.
Together with the proposed solution, details are given of a computer
system which has been implemented. The system was used by
textile designers for a real task. Prior to undertaking this work,
designers were interviewed in order to ascertain where colour played
an important role in their work and where it was found to be a problem.
A summary of the findings of these interviews together with a
survey of existing approaches to the problems of colour fidelity and
communication in colour computer systems are also given. As background
to this work, the topics of colour science and colour imaging
are introduced
A study of digital camera colorimetric characterisation based on polynomial modelling
The digital camera is a powerful tool to capture images for use in image
processing and colour communication. However, the RGB signals generated by a
digital camera are device-dependent, i.e. different digital cameras produce different
RGB responses for the same scene. Furthermore, they are not colorimetric, i.e. the
output RGB signals do not directly correspond to the device-independent tristimulus
values based on the CIE standard colorimetric observer. One approach for deriving a
colorimetric mapping between camera RGB signals and CIE tristimulus values uses
polynomial modelling and is described here. The least-squares fitting technique was
used to derive the coefficients of 3× n polynomial transfer matrices yielding a modelling
accuracy typically averaging 1 Δ E units in CMC(1:1) when a 3× 11 matrix is used.
Experiments were carried out to investigate the repeatability of the digitising system,
characterisation performance when different polynomials were used, modelling
accuracy when 8-bit and 12-bit RGB data were used for characterisation and the number
of reference samples needed to achieve a reasonable degree of modelling accuracy.
Choice of characterisation target and media and their effect on metamerism have been
examined. It is demonstrated that a model is dependent upon both media and colorant
and applying a model to other media/colorants can lead to serious eye-camera
metamerism problems