**Graphics recognition**.
It is a subfield of document analysis and understanding. It deals with
symbols, charts, diagrams, logos, etc. Some outstanding applications of
graphics recognition are the matching of fingerprints, the interpretation
of flow charts and diagrams, the analysis of musical scores for conversion
to MIDI, the conversion of engineering designs to a CAD-compatible representation,
the interpretation of architectural drawings, the analysis of maps in GIS
environents, the interpretation of electronic circuit diagrams, etc. My
current research is concerned about one of the central problems of graphics
recognition: symbol recognition. I have stated the problem in terms of
a graph matching formulation. The algorithms have been developed for an
architectural drawings understanding application (see further information
in the HDICAD
homepage).

**Structural pattern recognition**.
This is a field started at the end of 1960's and the beginning of the 1970's.
Nowadays, it is still an active area of research and a number of applications
have been done and are progressing using these techniques. The basis of
the structural methods is the relational organization of low-level features
into higher-level structures. This relational organization is represented
by means of symbolic data structures like strings, trees, graphs or arrays
instead of vectors of numbers that are used in the statistical pattern
recognition approach. These data structures also allow a hierarchical organization
of the information. Thus, two major attributes define the structural pattern
recognition field, namely, a hierarchical structure of a pattern in terms
of simpler subpatterns, and a set of relations which may exist between
different subpatterns. I am currently working on two particular problems:

** Inference of structural
models**. One of the fields where structural pattern recognition has
an intensive action is structural texture analysis. A structural texture
is characterized by a repetitive element called texel repeated according
to a set of placement rules. Graph-based formal grammars are useful structures
to represent such repetitive structures. Two problems arise, namely, texture
recognition and the inference of a structural model for texture representation.

J. Lladós, J. López-Krahe,
E. Martí. *A Hough-based method for hatched pattern detection in
maps and diagrams*. International Conference on Document Analysis and Recognition
(ICDAR'99). Bangalore (India), 20-22 september, 1999. *Accepted*.

J. Lladós, F. Lumbreras,
X. Varona. *A multidocument platform for automatic reading of identity cards*.
VIII National Symposium on Pattern Recognition and Image Analysis. Bilbao,
1999. *Accepted*.

J. Lladós, G. Sánchez,
E. Martí. *A string-based method to
recognize symbols and structural textures in architectural plans*.
Graphics Recognition, Algorithms and Systems. K. Tombre and A.K.Chhabra (eds).
Lecture Notes in Computer Science, 1389, pp. 91-103. Springer-Verlag, 1998.

J. Lladós, H. Bunke, E. Martí.
*Finding rotational symmetries by cyclic string
matching*, Pattern Recognition Letters, 18(14):1435-1442, 1997.

J.Lladós, *Combining
Graph Matching and Hough Transform for Hand-Drawn Graphical Document Analysis.
Application to Architectural Drawings *, PhD
Dissertation, November, 1997.

J. Lladós, G. Sánchez,
E. Martí. *A string-based method to
recognize symbols and structural textures in architectural plans*.
GREC'97 (2nd. IAPR Workshop on Graphics Recognition), Nancy (France), August,
1997.

G. Sánchez, J. Lladós,
E. Martí. *Segmentation and analysis
of lineal textures in plans*. VII National Symposium on Pattern Recognition
and Image Analysis, CVC-UAB, Barcelona, 1997.

J. Lladós, E. Martí.
*Playing with error-tolerant subgraph isomorphism
in line drawings*. VII National Symposium on Pattern Recognition and
Image Analysis, CVC-UAB, Barcelona, 1997.

J. Lladós, J. López-Krahe,
E. Martí, *A system to understand hand-drawn
floor plans using subgraph isomorphism and Hough transform*, Machine
Vision and Applications, 10(3):150-158, 1997.

J. Lladós, H. Bunke, E.
Martí, *Using cyclic string matching
to find rotational and reflectional symmetries in shapes*. Intelligent
Robots - Sensing, modeling and planning. R.C. Bolles, H. Bunke, H. Noltemeier
(eds), pp. 164-175, World Scientific, 1997.

J.Lladós, J. López-Krahe,
E. Martí, *Hand Drawn Document Understanding
Using the Straight Line Hough Transform and Graph Matching*, 13th.
International Conference on Pattern Recognition, Viena (Austria), 1996.

J.Lladós, *Interpretació
de dibuixos lineals fets a ma alçada mitjancant isomorfisme entre subgrafs
i transformació de Hough*, CVC Technical Report #010, March
1996.

J.Lladós, *Interpretacio
de dibuixos lineals mitjancant tecniques d'isomorfisme entre grafs*,
I Trobada de Joves Investigadors, Bellaterra (Barcelona), 1995.

J.Lladós, E.Martí,
*Structural recognition of hand drawn floor
plans*, VI National Simposium on Pattern Recognition and Image Analysis,
Cordoba, 1995.

J.Lladós, E.Martí,
J.Regincós *Interpretacion de diseños
a mano alzada como técnica de entrada a un sistema CAD en un ámbito
de arquitectura*, III National Conference on Computer Graphics, Granada,
1993.

** **