Bull's Head and Mermaid - The Bernstein Project - Österreichische ...
Bull's Head and Mermaid - The Bernstein Project - Österreichische ...
Bull's Head and Mermaid - The Bernstein Project - Österreichische ...
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Component model <strong>The</strong>saurus<br />
elongated to the jaw elongated to the muzzle / mouth<br />
stem rod<br />
bevel oblique<br />
2-lobed flower or leaf two-petalled<br />
4-lobed flower or leaf quatrefoil<br />
templar’s cross maltese cross<br />
threefoil trefoil<br />
brokeness brokenness / angularity<br />
curl noch nicht im <strong>The</strong>saurus<br />
alignment noch nicht im <strong>The</strong>saurus<br />
lateral noch nicht im <strong>The</strong>saurus<br />
<strong>The</strong> final revision of the trilingual <strong>The</strong>saurus was undertaken<br />
by comparing it with the main motif groups of Briquet.<br />
More than thirty terms that had not yet been recorded<br />
were added to the <strong>The</strong>saurus: amphora (amphore; Amphore),<br />
board game (damier; Brettspiel), dolphin (dauphin;<br />
Delphin), bagpipe (cornemuse; Dudelsack), lizard (lézard; Eidechse),<br />
sickle (faucille; Sichel), c<strong>and</strong>lestick (ch<strong>and</strong>elier;<br />
Kerzenleuchter), currycomb (étrille; Striegel), to name just a<br />
few. In addition, terms that were already included had to be<br />
adapted, as for example “escargot” (snail), which the <strong>The</strong>saurus<br />
had already listed as “limarçon”. <strong>The</strong> importance of<br />
editorial supervision can also be seen here, as the later<br />
change also had to be taken into account in Piccard-Online.<br />
Through the editorial work sketched above, the <strong>The</strong>saurus<br />
now includes 725 terms, in German, English, <strong>and</strong><br />
French, that represent the key vocabulary needed to describe<br />
watermarks. <strong>The</strong> advantage of the <strong>The</strong>saurus is clear:<br />
watermarks with the same motif can now be described<br />
with equivalent terms in English, German, <strong>and</strong> French,<br />
which fulfils the conditions needed for comprehensive<br />
searches in the various databases. In the framework of the<br />
project, a PDF-file of the trilingual <strong>The</strong>saurus has been<br />
made available on the <strong>Bernstein</strong> homepage so that research<br />
in all three languages is now possible.<br />
Literature: Palmer, Verbalizing Watermarks; Kämmerer,<br />
Städtewappen.<br />
E.F. (C.P.-K.)<br />
Digital Watermark Detection <strong>and</strong> Retrieval<br />
Introduction<br />
Watermarks <strong>and</strong> paper features are important sources of information<br />
to determine the dating <strong>and</strong> authenticity of incunabula<br />
<strong>and</strong> artworks. For instance it is possible to determine<br />
the artist <strong>and</strong> creation date of an artwork by discovering<br />
identical pieces of paper. Assume e.g. two etchings of<br />
Rembr<strong>and</strong>t. <strong>The</strong> one has been printed in 1648 <strong>and</strong> the other<br />
has an unknown date. However, since both have been<br />
made on the same paper, it is reasonable to suppose that<br />
also the other one has been made in 1648. <strong>The</strong> reason is<br />
that in the 16 th -18 th century paper was sold in stocks of paper<br />
sheets coming from the same paper mill <strong>and</strong> mould,<br />
which implies an identical paper structure <strong>and</strong> watermark.<br />
For that very reason watermarks <strong>and</strong> paper structures are<br />
collected all over the world by national libraries, archives,<br />
museums <strong>and</strong> art historical institutes, <strong>and</strong> watermark catalogues<br />
are published everywhere.<br />
Until now most collections of watermarks are in the form<br />
of line-drawings, rubbings, backlight <strong>and</strong> x-ray imagery. A<br />
part of them are now digitized. In the <strong>Bernstein</strong> project one<br />
tries to combine these digital databases to one large virtual<br />
repository of watermarks. As a matter of fact this will be a<br />
very powerful help for experts in the field of (art) history<br />
<strong>and</strong> incunabula. However, the generation of all these digital<br />
databases is an enormous task if it should be done manually.<br />
And furthermore, the question is: when this large database<br />
is available how to find the appropriate information<br />
searched for? At the Delft University of Technology, research<br />
is performed how far the usage of computers can<br />
assist in these complex tasks. In this paper some examples<br />
are given.<br />
Watermark detection<br />
Before a computer can h<strong>and</strong>le imagery of watermarks all<br />
the line-drawings, rubbings, backlight <strong>and</strong> x-ray images<br />
should be in a digital form. In practice this means that each<br />
picture element (the so-called pixel) should be represented<br />
by a number, in general between 0 <strong>and</strong> 255, representing<br />
the grayscale values of the various picture elements. At this<br />
moment most of the new watermark images are digitized<br />
directly, since most of the present image generation techniques<br />
are digital. In case of printed watermarks <strong>and</strong> ‘analogue’<br />
photographs they should be digitized first. Until now<br />
watermark extraction was primarily be done manually by<br />
using transparencies <strong>and</strong> tracing off with as a result a linedrawing.<br />
In fact it simple, but taking into account the large<br />
amount of watermarks a tedious drudgery. Furthermore, as<br />
a matter of fact the final result is not exact <strong>and</strong> differs<br />
sometimes a little bit from the original real watermark.<br />
However, for a computer watermark extraction is a complex<br />
task (with the exception of binary imagery which only has<br />
black <strong>and</strong> white pixels). Considering the X-ray images they<br />
are in general very noisy. This holds especially for 16 th <strong>and</strong><br />
17 th century paper. Ill. 10 gives an example; even for the expert<br />
it is difficult to determine which points belong to the<br />
watermark <strong>and</strong> which ones do not. And this holds the more<br />
for the computer since it has only a huge amount of numbers,<br />
representing the image, <strong>and</strong> in which it should detect<br />
the watermark pixels.<br />
Our goal is the development of a method which could<br />
detect automatically as many watermarks as possible without<br />
any user interaction. <strong>The</strong> basic idea is that watermarks<br />
are formed by lines <strong>and</strong> have specific properties. In the<br />
present case we considered five properties:<br />
a) the line profile: the one-dimensional representation of<br />
the section in terms of intensity,<br />
b) the line contrast: the contrast difference with the background,<br />
c) the line width,<br />
d) the spatial connectivity: lines exist from connected<br />
points,<br />
e) <strong>and</strong> the line length.<br />
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