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VOL. 10, NO. 15, AUGUST 2015 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2015 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
6410
GLCM TEXTURE ANALYSIS ON DIFFERENT COLOR SPACE FOR
PTERYGIUM GRADING
Mohd Zulfaezal Che Azemin1, Mohd Izzuddin Mohd Tamrin2, Mohd Radzi Hilmi1 and
Khairidzan Mohd Kamal3
1Kulliyyah of Allied Health Sciences, International Islamic University Malaysia, Kuantan, Malaysia
2Kulliyyah of ICT, International Islamic University Malaysia, Gombak, Malaysia
3 Kulliyyah of Medicine, International Islamic University Malaysia, Kuantan, Malaysia
ABSTRACT
GLCM texture features have been widely used to characterize biomedical images. Most of the previous studies
using GLCM features to characterize biomedical images only consider single or limited color space due to the use of only
one color model. To mimic human color perception, conventional RGB color model may need to be supplemented with
other color space models for better human vision representation. This study is aimed to find an optimal set of GLCM
features extracted from different color space for pterygium grading. Mimicking human color perception has commonly
employed RGB color space, which is shown in this paper is inadequate. GLCM features when extracted in various color
space show better representation of human perception (correlation coefficient > 0.6) compared to using RGB color space
(correlation coefficient < 0.2).
Keywords: GLCM texture, biomedical, pterygium grading.
INTRODUCTION
A measurable system for looking at pixel
composition that regards the spatial associations of pixels
is known as Gray-Level Co-occurrence Matrix (GLCM)
[1]. The matrix representation operates as textural
descriptor by ascertaining how frequently a pixel sequence
matches with a particular pattern exists in a two-
dimensional image, generating a GLCM. Features based
on statistical formula can further be applied on GLCM to
quantify the texture pattern of the image, for example,
correlation and homogeneity analyses.
GLCM texture features have been widely used to
characterize biomedical images. Previous researches
include classification of benign and malignant liver tumors
[2], lung image registration [3], diagnosis in breast MRI
images [4], identification of lobar fissure regions [5], and
in the classification of epithelial pre-cancer cells [6].
Most of the previous studies using GLCM
features to characterize biomedical images only consider
single or limited color space due to the use of only one
color model. To mimic human color perception,
conventional RGB color model may need to be
supplemented with other color space models for better
human vision representation. Previous studies have shown
that different color space is more perceptually relevant
depending upon its applications [7]. Prior research works
using different color space mostly focus on solving image
segmentation problems [8–10].
Tissue redness has been an important indicator in
assessing and diagnosing disease [11–13]. The importance
of automating the redness grading has been highlighted
previously particularly due to low intra-graders
repeatability [14]. However, there is a lack of research to
employ GLCM features on different color space to mimic
human clinical grading. This study is aimed to fill the gap
in the literature.
MATERIALS AND METHODS
A total of 68 eye images affected by pterygium
are captured with slit lamp bio microscopy using a
diffused white light. Figure-1 shows the images with their
respective grades labelled by a clinician. The region of
interest is from the apex of the pterygium to the limbus as
shown in the Figure-1(a). The grading is treated as a
continuous variable.
Figure-1. Pterygium grading based on the tissue redness.
(a) Grade 1.0, (b) Grade 1.5, (c) Grade 2.0, (d) Grade 2.5,
(e) Grade 2.5, (f) Grade 3.0.
VOL. 10, NO. 15, AUGUST 2015 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2015 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
6411
The previous research [14] used RGB colour
space model as their feature for texture analysis. In this
paper, 14 different colour space models are employed as
the features for evaluating the quality of pterygium
grading. The full list of the colour spaces is available from
Table-1.The motivation of using these colour space
models is to mimic the real perception of human expert in
evaluating these images for grading the pterygium.
Table-1. List of color space used in this work.
The steps undertaken to extract these features using these
colour spaces are summarized in Figure-2. For every
image and its selected region of interest that are marked
for pterygium grading are retrieved in Red, Green and
Blue colours. Next, the Matlab Toolbox developed by
Pascal [15] is used for converting this image from the
RGB colour model to the other 14 colour space models. A
matrix is created to split every colour spaces into its 3
components. The total number of textures for the entire
colour space models that are produced for each image is
168. Following this, only the selected region of interest
are considered for the conversion to GLCM and the
remaining pixels residing outside these area are assigned
as not a number (NaN).
Figure-2. Flow chart on extracting features based on
GLCM properties.
Figure-3 demonstrates the conversion to GLCM.
The value of each pixel is set between the ranges of 1 to 8,
which indicates the level of intensity for each colour
component in the image. The spatial relationship between
each pixel from the region of interest is determined by
calculating the frequency of the intensity of that pixel in i
against its adjacent pixel in j.
Figure-3. The construction of GLCM (right) from a
hypothetical image with varying intensity (left).
VOL. 10, NO. 15, AUGUST 2015 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2015 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
6412
For example, in Figure-3, the value 2 in element
(7,7) from the GLCM is the total sum of co-occurrence
between the adjacent pixels with the same intensity of 7
throughout the image. The algorithm will scan from these
pixels from left to right until it reaches the end of the
pixel. The remaining elements from the GLCM have the
value of 1 and 0 because the sum of co-occurrence
between its respective adjacent pixels is 1 or 0.
The GLCM produced is used to statistically
examine spatial distribution of the pixels’ intensity levels
in this image. The statistical analyses employed for the
texture analysis are contrast, correlation, energy,
homogeneity. The details on these statistical properties
are described below.
Contrast measures the differences in intensity
between a pixel against the remaining pixels in the image.
It is defined as,
Contrast =
where p(i,j) is the position of the GLCM in that the value
represent the sum of co-occurrence between adjacent
pixels of i and its neighbour j.
Correlation measure the level of correlations
between a pixel against the remaining pixels in the image.
It is defined as,
Correlation =
Energy measure the summation of squared
element in the entire GLCM. It is formulated as,
Energy = .
Homogeneity measure the similarity in the
variation of the distribution in the GLCM against the
diagonal of the matrix. It is defined as,
Homogeneity = .
RESULTS
Figure-4 shows the results of correlation analysis
between the GLCM features and scores from the human
grading. Four features are identified as good features with
correlation coefficients more than 0.6. The features are
GLCM-Contrast (Pr component of Y’PbPr color space),
GLCM-Energy (Pr component of Y’PbPr color space),
GLCM-Homogeneity (Pr component of Y’PbPr color
space), and GLCM-Energy (V component of Y’UV color
space). The features extracted from conventional RGB
color space perform poorly with correlation coefficients
less than 0.2.
Figure-4. Correlation between human grading and the
GLCM features extracted from images with different color
space.
CONCLUSIONS
This research work identifies a set of good
GLCM features that can be used in the future on modeling
human perception of tissue redness. It has been proven
that GLCM features extracted from conventional RGB
color space are not sufficient and must be supplemented
with features in other color space. GLCM features when
extracted in various color space show better representation
of human perception (correlation coefficient > 0.6)
compared to using RGB color space (correlation
coefficient < 0.2).
However, with a single feature, the best GLCM
feature can only account for 49.63% (from r-squared
analysis) variability of the human grading. Fusion of
multiple features is warranted to produce a better model of
pterygium grading. Experiments with different type of
textural features which include fractal dimension [16, 17]
may also further be tested in future research.
REFERENCES
[1] Baraldi A. and Parmiggiani F. 1995. Investigation of
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[2] Xian G.M. 2010. An identification method of
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[3] Park S., Kim B., Lee J., Goo J.M. and Shin Y.G.
2011. GGO nodule volume-preserving nonrigid lung
registration using GLCM texture analysis. IEEE
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[4] Yachun P., Yuanzhi S. and Li L. 2010. Breast lesion
classification on MRI by texture features. 2nd
VOL. 10, NO. 15, AUGUST 2015 ISSN 1819-6608
ARPN Journal of Engineering and Applied Sciences
©2006-2015 Asian Research Publishing Network (ARPN). All rights reserved.
www.arpnjournals.com
6413
International Conference on Information Science and
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