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Experimental Comparison of Segmentation Algorithms

on Images of Heat-Emitting Objects and Methods for

Their Accuracy Improvement

Tomasz Koszmider, Marcin Bkaa, Anna Fabijaska, Krzysztof StrzechaAbstract In this paper problem of accurate segmentation of

images presenting melted specimens of metal is considered.

Firstly the theory of thermal phenomena influence on recorded

images is explained. A review of most popular edge-based

segmentation methods is provided. Results of applying drop

shape analysis algorithm to segmented images are presented,

analyzed and discussed.

Keywords edge detection, image segmentation, gradient

operators, high temperatures, drop shape, image processing.

I. INTRODUCTION

At high temperatures the strong thermal radiation causesan aura phenomenon or reflection effect in areas around the

specimen and base-plate contact points (Fig. 1) [1]. It results

with an incorrect classification of background pixels into

a set of points representing the object.

Fig. 1 Results of inaccurate approximation of probe edge.

The main goal of experimental comparison of

segmentation algorithms was to choose the most suitable

method to be applied in Thermo-Wet system which was

developed to calculate surface tension and contact angle of

melted specimens of metal [2].

II. METHOD OF COMPARISON

The comparison of segmentation methods was performed

using four most popular algorithms which were: Canny,

Sobel, LOG and LOG2 (where LOG2 denotes LOG

preceded by double Gaussian filtration).

The set of test images was taken from Thermo-Wet vision

system during measurements of contact angle and surface

tension of different metal probes (Fig. 2).

Fig. 2 Image of melted metal in temperature above 1010C.

Fig. 3 Binary representation of probe edge.

The goal of segmentation process was to obtain binary

representation of drop edge (Fig. 3). To verify accuracy of

segmentation algorithms drop shape analysis was performed

on edges segmented using the considered methods. It aimed

at calculating drop maximum width and height (Fig. 4).

____________________________________________________________

Tomasz Koszmider, Marcin Bkaa, Anna Fabijaska,

Krzysztof Strzecha Department of Computer Engineering,

Technical University of Lodz, 18/22 Stefanowskiego Str.,

Lodz, 90-924 Lodz, POLAND, E-mails: {t.koszmider,

m.bakala, an_fab, strzecha,} @kis.p.lodz.pl

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Fig. 4 Drop geometric parameters: d - maximum width, h

maximum height.

III. RESULTS

Determined values of drop geometric parameters obtained

for all tested segmentation algorithms for images of different

specimens are presented in the Tables 1-5.

The first column of each table contains the name of the

segmentation algorithm used. The second and the third

column contain determined values of drop maximum width

and height respectively. The dimensions are given in pixels.

The first row contains values of geometric parameters

calculated on based on edge determined by segmentation

algorithm implemented in the previous version of Thermo-Wet system measurement software.

TABLEI

PROBE OF COPPER IN 1000C

Proper values 227,74 102,92

Canny 234,49 106,23

LOG 235,06 106,22

LOG2 232,98 95,58

Sobel 194,84 107,89

TABLEIIPROBE OF COPPER IN 1100C

Proper values 222,1 101,95

Canny 230,73 104,19

LOG 229,76 94,8

LOG2 229,7 94,22

Sobel 230,81 104,45

TABLEIII

PROBE OF STEEL IN 1300C

Proper values 116,67 61,8

Canny 124,77 66,81

LOG 292,01 21,26

LOG2 124,74 65,74

Sobel 124,22 66,17

TABLEIVPROBE OF STEEL IN 1400C

Proper values 116,25 62,14

Canny 124,7 65,42

LOG 149,75 14,27

LOG2 133,88 14,34

Sobel 124,66 66,64

TABLEV

PROBE OF GOLD IN 1080C

Proper values 183 104,92

Canny 200,35 105,68

LOG 190,45 104,12

LOG2 190,99 103,67

Sobel 186,07 99,99

IV. CONCLUSIONS

Unfortunately all tested segmentation algorithms have

serious problem with proper identification of areas where

strong aura effect occurs. In almost all cases these areas are

identified as a part of probe and base. It results with higher

values of calculated geometric parameters and inconsequence increase the real size of the drops. The best

results produces Sobel filtering algorithm which with some

modifications could be the suitable solution for the Thermo-

Wet system measurement software.

V.ACKNOWLEDGMENT

This paper presents research sponsored by the Ministry of

Science and Higher Education of Poland, project no. N

N519 403037.

REFERENCES

[1] D. Sankowski, K. Strzecha, S. Jezewski, J. Senkara, andW. Lobodzinski, Computerised Device with CCD

Camera for Measurement of Surface Tension and

Wetting Angle in Solid-Liquid Systems, in 16th IEEE

Instrumentation and Measurement Technology

Conference IMTC, Venice, Italy, May 1999, pp. 164-

168.

[2] A.M. Emelyanenko, and L.B. Boinovich, The Use of

Digital Processing of Video Images for Determining

Parameters of Sessile and Pendant Drops, Colloid

Journal, vol. 63(2), pp. 159-172, 2001.