## ANNOUNCEMENT: Parallel Algorithms for Image Enhancement and Segmentation

### ANNOUNCEMENT: Parallel Algorithms for Image Enhancement and Segmentation

ANNOUNCEMENT:

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Parallel Algorithms for Image Enhancement and Segmentation by
Region Growing with an Experimental Study
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We have released our technical report entitled Parallel Algorithms
for Image Enhancement and Segmentation by Region Growing with an
Experimental Study,'' by David A. Bader, Joseph Ja'Ja', David Harwood,
and Larry S. Davis. Technical Report Number: CS-TR-3449 and
UMIACS-TR-95-44. Institute for Advanced Computer Studies (UMIACS),
University of Maryland, College Park, May 1995.

The paper is available in HTML and PostScript format via WWW:

or via anonymous ftp to:

ftp://ftp.cs.umd.edu/pub/papers/papers/3449/3449.ps.Z

If you prefer a hardcopy, please reply to this message and send me

ABSTRACT:
This paper presents efficient and portable implementations of a
useful image enhancement process, the Symmetric Neighborhood Filter
(SNF), and an image segmentation technique which makes use of the SNF
and a variant of the conventional connected components algorithm which
we call delta-Connected Components. Our general framework is a
single-address space, distributed memory programming model. We use
efficient techniques for distributing and coalescing data as well as
efficient combinations of task and data parallelism. The image
segmentation algorithm makes use of an efficient connected components
algorithm which uses a novel approach for parallel merging. The
algorithms have been coded in Split-C and run on a variety of
platforms, including the Thinking Machines CM-5, IBM SP-1 and SP-2,
Cray Research T3D, Meiko Scientific CS-2, Intel Paragon, and
workstation clusters. Our experimental results are consistent with the
theoretical analysis (and provide the best known execution times for
segmentation, even when compared with machine-specific
implementations.) Our test data include difficult images from the
Landsat Thematic Mapper (TM) satellite data. More efficient
implementations of Split-C will likely result in even faster execution
times.

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Electrical Engineering Department
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FAX:    301-314-9658

Hello everybody,

Does anyone know if the following decision problem has an efficient
solving algorithm ?

Instance : An Image I described over grey-levels, two positive
Integers K,K'.

Question : Does there exists a partition of I into K connex regions $R_1, ..., R_K$ such that the between-regions error E of this partition
exceeds K' ?

Here, $E=\sum_{j=1}^{K} {|R_j|(\overline{R_j}-\overline{I})^2}$,
where $|R_j|$ is the cardinality (pixel number) of $R_j$,
$\overline{R_j}$ is the average grey-level of $R_j$, and
$\overline{I}$ is the average grey-level of $I$.

Should anyone know efficient algorithm for this problem (or the
optimization version, where the objective is find a valid partition
maximizing E, i.e. we remove K' from the instance), please give also
references I could use (even techreports).

Thanks a lot,

- Richard.