Robotics Reference
In-Depth Information
Figure 36.
Hue histograms of similarly coloured van Gogh paintings (Courtesy of Eric
Postma and Jaap van den Herik)
In order to analyse an artist's use of colour, two different types of
colour histogram have been investigated. A colour histogram is simply a
count of the relative frequencies of pixels of different colours, for exam-
ple an RGB histogram is based on the three primary colours: red, green
and blue. But raw RGB values are unsuitable for representing the percep-
tual appearance of colour, not surprising in view of the fact that humans
perceive colour in terms of its hue, its saturation and its intensity, rather
than in terms of its three RGB components. Figure 36 shows the hue
histograms of two van Gogh paintings,
Wheat Field under Threatening
Skies
and
The Church at Auvers-sur-Oise
, and the two pairs of coinciding
peaks in these histograms suggest a clear link between the two paintings.
Early results with Authentic have been encouraging. The Maastricht
group's initial quest for good features yielded sufficient of them to enable
the successful classification of 60 impressionist paintings,
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and many
more features remain to be tested. A group at the National University
of Singapore has found, for example, that the colouring of skin patches
is a useful identifying feature, in particular the transition from a light
colouration to a darker one when the arms and legs of the human subjects
are partly in the light and partly in the shade.
The initial conclusion of the Maastricht researchers is that within fifty
years the visual signature of painters will be as recognizable as those of
any handwritten signature.
In a similar project at Dartmouth College, New Hampshire, Hany
Farid and his team are using statistical techniques on the characteristic
strokes of an artist's brush, pen or pencil, to produce an “electronic sig-
nature” of each artist's style. Details of the direction, curvature, pressure
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These comprise ten paintings by each of six artists: Claude Monet, Vincent van Gogh, Paul
Cezanne, Alfred Sisley, Camille Pissarro and Georges Seurat.
