Upload
bartholomew-lyons
View
219
Download
1
Embed Size (px)
Citation preview
Image Segmentation&
Template Matching
Multimedia Signal Processing
lecture on 6.3.2007
Petri Hirvonen
Image Segmentation
Terminology
Image processing tools
Examples
Details of the Assignment
Tracking Rolling Leukocytes With Shape and Size Constrained Active Contours
Image segmentation based on maximum-likelihoodestimation and optimum entropy-distribution (MLE–OED)
Image segmentation problem is basically one of psychophysical perception, and therefore
not susceptible to a purely analytical solution.
Motivation: Image content representationRequirements: object definition & extraction
Mathematical morphology is very useful
for analyzing shapes in images.
Basic tools: dilation A+B and erosion A–B
Application: boundary detection
Internal boundary: A - (A–B)External boundary: (A+B) - A
Morphological gradient: (A+B) - (A–B)Assignment: object edges
A - (A–B) (A+B) - A (A+B) - (A–B)
Dilation:
Replace every point (x,y) in A with a copy of B centered at B(0,0)
The result D is the union of all translations.
Erosion:
The resulting set of points E consists ofall points for which B is in A.
0 0 0 0 0 0 1 1 0 0 0 1 1 0 0 0 1 1 0 0 0 1 1 1 0 0 0 1 1 0 0 0 0 0 0
1 0 1 0 1 0 1 0 1
0 1 0 1 1 1 0 1 0
A AD DE E
B B
Structuring element, kernel = B
Minkowski addition / subtraction
Image information
Segmenting SEM-images
max
min
)(&minargi
ikr
kbest pIpIkIDk
• Dilation of the thresholded block contains the thresholded gradient completely at the optimal threshold.
n
I
m
IGGI nm ,,
22nm GGM
(k and p are thresholds, D is dilationwith a structuring element of radius r)
max
min
)(&minargi
ikr
kbest pIpIkIDk
Information & colour
222
211_
2 groupwithin
2222
11_2
imageimagegroupbetween
• Nobuyuki Otsu, A Threshold Selection Method from Gray-Level Histograms, 1979
• For bimodal distributions
minimized
maximized
Histogram-based thresholdingOtsu’s method
kk
kkimagegroupbetween
1
2
_2
Probability of intensity k
Mean of group @ k
Hough transform Region Of Interest Histogram
)( 00 xxkyy 221
221 )()( yyxxd
Length and width are the perpendicular
distances on the original
(thresholded) target area.
Perimeter is computed by
the Chain Code algorithm.
Template Matching
f
h
),(),(),(),( * vuHvuFyxhyxf
)( *1 HFFc
We have first created a DATABASEthat contains the elements in the table.
FOR-loop is executed for all templatesFont_images{index}And the result is visualized in colours:
Scale ?Rotation ?
Object perimeter
Object perimeter