Shape from Positional-Contrast: Characterising Sketches with Qualitative Line Arrangements

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Springer Science & Business Media, Oct 10, 2007 - Computers - 214 pages
Graphical queries for the purpose of searching for pictorial information are of growinginterestinareaswherepicturesprovidevaluableinformation, including, for instance, design, architecture, and engineering. Sketching graphical queries is a natural way of revealing the visual appearance of objects one has in mind. The problem which arises is identifying necessary shape properties of sketches, thatis,thosepropertieswhicharenotaccidentalbutarenecessaryforspecifying a particular object property. This problem arises in particular because sketches are imprecise, and often distorted by the artistic limitations of the sketcher. From the theoretical point of view the concept of pictorial space applies. In this context, new concepts are required, in particular for dealing with imp- cise shape information in the plane. Taking into account constraints imposed by pictorial space, a relation algebra of intersection-free relations is proposed, which allows reasoning about qualitative line arrangements in the plane. The theory is further developed for characterising polygons, by deriving a number of qualitative properties which aid in describing polygons qualitatively. Applying this theory, only line arrangements which are both readily sketched and easily perceivable are considered to be di?erent. The notion of positional-contrast is introduced, which points out that the particular arrangements of line segments, i. e. their positions relative to each other, provide an expressive means of ch- acterising necessary shape properties. The method developed in this work is applied in using graphical queries to search for historical objects.
 

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Contents

Sketches
3
The imprecision of sketches 13
12
Qualitative line arrangements
43
Characterising polygons qualitatively 75
74
stances the numbers refer to the TLT12 relations
86
with respect to line segment x
102
Evaluation
133
Positionalcontrast
157
Weisser Sommercalvil
189
Weisser Winterkalvill
190
Zwei Jahre dauernde Renette
191
Zwiebelborsdorferapfel
192
B Queries and reference sets
193
The first query
194
The second sketch and its precision and recall
196
The third sketch and its precision and recall
198

A Bertuchcollection 165
164
Schwarzer Borsdorferapfel
184
Sommer Zuckerapfel
185
Veilchenapfel
186
Weiße Herbstkalville
187
Weißer Maatapfel
188
The fourth query
200
The fifth sketch and its precision and recall
202
The sixth query
205
Bibliography
209
Copyright

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Page xi - FIG. 2. Subjects attempted to approximate the closed figure shown above with a pattern of 10 dots. Radiating bars indicate the relative frequency with which various portions of the outline were represented by dots chosen. Evidence from other and entirely different situations supports both of these inferences. The concentration of information in contours is illustrated by the remarkably similar appearance of objects alike in contour and different otherwise. The "same...

About the author (2007)

Björn Gottfried hat in Hamburg und Bremen Informatik studiert,
arbeitet seit 1999 am Technologie-Zentrum Informatik an der Bremer Universität, hat im Jahre 2005 promoviert und bietet Lehrveranstaltungen zur Bildverarbeitung, zum Bildverstehen und zum Diagrammatischen Schließen an.

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