A calculation of colours: towards the automatic creation of graphical user interface colour schemes : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Computer Science at Massey University, Palmerston North, New Zealand
Interface colour scheme design is complex, but important. Most software allows users
to choose the colours of single items individually and out of context, but does not
acknowledge colour schemes or aid in their design. Creating colour schemes by picking
individual colours can be time-consuming, error-prone, and frustrating, and the results
are often mediocre, especially for those without colour design skills. Further, as colour
harmony arises from the interactions between all of the coloured elements, anticipating
the overall eff ect of changing the colour of any single element can be difficult.
This research explores the feasibility of extending artistic colour harmony models to
include factors pertinent to user interface design. An extended colour harmony model
is proposed and used as the basis for an objective function that can algorithmically
assess the colour relationships in an interface colour scheme. Its assessments have been
found to agree well with human evaluations and have been used as part of a process to
automatically create harmonious and usable interface colour schemes.
A three stage process for the design of interface colour schemes is described. In the
fi rst stage, the designer speci es, in broad terms and without requiring colour design
expertise, colouring constraints such as grouping and distinguishability that are needed
to ensure that the colouring of interface elements reflects their semantics.
The second stage is an optimisation process that chooses colour relationships to
satisfy the competing requirements of harmonious colour usage, any designer-specified
constraints, and readability. It produces sets of coordinates that constitute abstract
colour schemes: they de fine only relationships between coloured items, not real colours.
In the third and fi nal stage, a user interactively maps an abstract scheme to one
or more real colour schemes. The colours can be fi ne-tuned as a set (but not altered
individually), to allow for such "soft" factors as personal, contextual and cultural
considerations, while preserving the integrity of the design embodied in the abstract
scheme. The colours in the displayed interface are updated continuously, so users can
interactively explore a large number of colour schemes, all of which have readable text,
distinguishable controls, and conform to the principles of colour harmony.
Experimental trials using a proof-of-concept implementation called the Colour Harmoniser
have been used to evaluate a method of holistic colour adjustment and the
resulting colour schemes. The results indicate that the holistic controls are easy to
understand and eff ective, and that the automatically produced colour schemes, prior
to fi ne-tuning, are comparable in quality to many manually created schemes, and after
fi ne-tuning, are generally better.
By designing schemes that incorporate colouring constraints specifi ed by the user
prior to scheme creation, and enabling the user to interactively fi ne-tune the schemes
after creation, there is no need to specify or incorporate the subtle and not well understood
factors that determine whether any particular set of colours is "suitable".
Instead, the approach used produces broadly harmonious schemes, and defers to the
developer in the choice of the fi nal colours.