TEXTURE IMAGE ANALYSIS USING LBP AND DATA
COMPRESSION
Nuo Zhang and Toshinori Watanabe
Graduate School of Information Systems, the University of Electro-Communications,
1-5-1, Chofugaoka, Chofu-shi, Tokyo, Japan
Keywords:
Data Representation, Texture Image, Data Compression, Local Binary Patterns.
Abstract:
Texture classification is an important technology widely applied in many application fields in image process-
ing. In this study, a novel representation method for texture image is proposed. The proposed approach is
based on the consideration of using data compression to search the essential feature of frequent pattern in
texture images. Furthermore, to deal with the difficult situation caused by different situations of photography,
local binary pattern (LBP) is introduced to the proposed approach to reduce the numbers of varieties of pat-
terns in texture image. Compresibility vector space is adopted in this study instead of learning phase. Based
on the patterns extracted by LBP operator which are invariant to monotonic gray-level transformations, data
compression helps extract the longest and frequent features. These features provide high analytical ability for
texture image. The simulation results will show good performance of our approach.
1 INTRODUCTION
Textures, such as the surface of wood and rock gener-
ally appear in most images in real world. The related
algorithms for texture analysis have been broadly
studied so far. Exact feature expression of texture im-
age will help to improve the performance in image
processing.
A lot of methods for the analysis of texture im-
age have been proposed. Hu Chun-hai et al. fo-
cused on the analysis of wood surface inspection to
wood machining industries (Hu and Liang, 2008).
They presented an efficient image restoration scheme
in wavelet domain and defect detection approach for
texture image. Retrieval of texture image attracts
researchers and a lot of results have been emitted.
Ying Liu et al. proposed a image retrieval method
based on texture segmentation in wavelet domain (Liu
et al., 2003). And this method showed promising re-
trieval performance based on texture features. Fauzi,
M.F.A. et al. presented a robust technique for texture-
based image retrieval in multimedia museum collec-
tions (Lewis, 2003). And the results showed that the
multiscale sub-image matching method is an efficient
way to achieve effective texture retrieval without any
segmentation. Smith, J.R. et al. proposed a new al-
gorithm for the automated extraction and indexing
of salient image features based on texture features
(Smith and Chang, 1996). Suzuki, M.T. et al. used
Laws’ texture energy measure technique to analyze
texture image (Suzuki et al., 2009). They used multi-
ple resolutions of filters to make it possible to extract
various image features from 2D texture images of a
database. In texture analysis, a difficult problem is
that textures are often not uniform, due to changes in
monotonic gray-level, orientation, scale or other vi-
sual appearance.
In this study, a new representation method for tex-
ture image based on the combination of local binary
patterns (LBP) (Ojala et al., 2002) and data com-
pression is introduced. The proposed approach can
find long and frequent patterns, which are invariant
to monotonic gray-leveltransformations, from texture
images and use shorter symbols to replace them. This
manner suggests that the proposed approach is able to
be used as a effective method for texture image repre-
sentation. The performance of the proposed approach
will be shown in experiments.
2 IMAGE REPRESENTATION
USING LBP OPERATOR AND
DATA COMPRESSION
In this study, we attempt to build a feature space
(compressibility space) to represent texture images
appreciatively. We first convert the input texture im-
437
Zhang N. and Watanabe T..
TEXTURE IMAGE ANALYSIS USING LBP AND DATA COMPRESSION.
DOI: 10.5220/0003850904370440
In Proceedings of the International Conference on Computer Vision Theory and Applications (VISAPP-2012), pages 437-440
ISBN: 978-989-8565-03-7
Copyright
c
2012 SCITEPRESS (Science and Technology Publications, Lda.)
ages to ones which are robust to monotonic gray-level
transformations. Then, some images are randomly
selected to build a feature space. The flow chart is
shown in Fig. 1.
In general, a model of input information source
is used for encoding the input stream in data com-
pression. And a compression dictionary is used as the
model. The compression dictionary is automatically
produced when compressing input data, eg. Lempel-
Ziv (LZ) compression (Ziv and Lempel, 1978). In the
same way, the proposed approach constructs a com-
pression dictionary by encoding input data forms. It
makes a compressibility vector space from the com-
pression dictionary to project new input data into it.
Therefore, we can get the feature of data represented
by a compressibility vector. Finally, input data are
classified by analyzing these compressibility vectors.
Figure 1: Representation of image based on LBP and data
compression.
To avoid the effect of monotonic gray-level trans-
formations in real world texture images, local binary
pattern (LBP) (Ojala et al., 2002) is employed in
the proposed approach before the construction of the
compressibility space. It is considered to be invari-
ance against monotonicgray-leveltransformations af-
ter an image is processed by LBP.
2.1 Local Binary Pattern
The LBP operator was originally developed for tex-
ture description (Ojala et al., 2002). It assigns each
pixel a binary value in comparison with the center
pixel intensity in a local neighborhood. If the gray-
level of a neighboring pixel is equal to or larger than
that of the central pixel, the value of that pixel is set
Figure 2: The circular (8,1), (16,2), and (8,2) neighbor-
hoods. The pixel values are bilinearly interpolated when-
ever the sampling point is not in the center of a pixel.
to one, otherwise zero. Then, LBP operator sums up
the value of neighborhood:
LBP
R
,
P
(x, y) =
P1
i=0
s(p
i
p
c
)2
i
, s(x) =
0,x<0
1,x 0
(1)
where p
c
corresponds to the gray-level of the center
pixel of a local neighborhood, and p
i
corresponds to
the gray-levels of P sampled pixels on a circle of ra-
dius R. The notation (P, R) stands for pixel neighbor-
hood which means P sampling points on a circle of
radius R. Since correlation between pixels decreases
when distance increases, most texture informationcan
be obtained from local neighborhood. Thus, the ra-
dius R is usually kept small.
Then, the histogram of the processed image is
investigated instead of original texture image (Fig.
2). During which, bilinear interpolation is used when
sampling points do not fall in the middle of a pixel.
See Fig. 2 for examples of circular neighborhoods.
According to the robustness to monotonic gray-
level transformations of LBP descriptor, we employ
LBP descriptor before the construction of compress-
ibility vector space. For effectively representing fea-
tures in a texture image, the image result processed
by LBP descriptor instead of LBP histogram, is used
in this study. In comparison with the original image,
there are fewer but normalized patterns in the image
result processed by LBP descriptor. These patterns
helped to find the same features between two pho-
tos of one person’s face took in different time periods
and showed high representing performance. Instead
of histograms used in original LBP method, the im-
age results processed from LBP descriptor are then
used to construct a feature space.
2.2 PRDC-based Image Representation
The proposed approach for image representation is
described as follows. The flow chart is shown in Fig.
1.
Each image is processed by LBP operator. The
image consists of local binary patterns is filtered by a
step functionand pixel sub-sampling, in consideration
of the computation cost for the following processing.
VISAPP 2012 - International Conference on Computer Vision Theory and Applications
438
In this study, grayscale images are used in the exper-
iments. All the images are changed to 256 grayscale
in a pre-process step. Then a step function is used on
these grayscale images to reduce the 256 gradation
into 16. And the m× n image is converted to a 1× mn
vector. Text compression is used by PRDC (Pattern
Representation Scheme using Data Compression) to
find most frequently repeated and longest feature in
text data. In order to adopt this advantage of PRDC,
images converted to text data. But the size of image
data is too big to directly convert each pixel to a char-
acter. Besides that the extracted features will become
too much and some of which are redundancy. Hence,
we consider dividing a 1 × mn vector segments and
cluster them. After which, each cluster is replaced
by a character and the converted image is called text-
transformed image. To obtain the text-transformed
images, data compression is then used for representa-
tion of the converted texture image in this study. Each
1× mn vector (of a grayscale image) is made into seg-
ments with length L. The PRDC is used to compress
the segments into compressibility vectors. The dictio-
naries used for compression are constructed by com-
pressing the pre-processed images with LZW method,
from a small number of randomly chosen images.
On these compressibility vectors, clustering with
k-means is performed to get clusters of segments. It
is considered that the segments belong to the same
cluster have similar properties. Therefore we can re-
place them by one character, from which we get the
text-transformed image.
Now we classify the text-transformed images
based on the PRDC. The PRDC is used again to com-
press the text-transformed image to obtain compress-
ibility vectors. And the dictionary is constructed by
compressing the text-transformed image with LZW
method. In the same way, clustering is performed on
the compressibility vectors. The compressibility vec-
tors are used as follows for classification of similar
texture image. The compression dictionaries consti-
tute a compressibility vector space. The compressibil-
ity vector space can be represented by a compressibil-
ity table, which is made by projecting the input data
into the compressibility vector space. Let N
i
be the
input data. By compressing the input data, a com-
pression dictionary is obtained, which is expressed as
D
N
i
. Compressing data N
j
by D
N
i
, we get compres-
sion ratio C
N
j
D
N
i
=
K
N
i
L
N
j
. Where, L
N
j
is the size of the
input stream N
j
, K
N
i
is the size of the output stream.
Compressing with all of the dictionaries, we obtain a
compressibility vector for each input and for all input
data we get a compressibility table. In this table, the
columns show the data N
j
, the rows show the com-
pression dictionary D
N
j
formed by the same data, and
the elements show the compressibilityC
N
j
D
N
i
[%]. We
utilize this table to characterize data. Finally, images
are classified by the proposed approach.
3 EXPERIMENTS AND RESULTS
In this section, we show how to evaluate the perfor-
mance of the proposed approach. Experiments with
using real-world images were carried out. When eval-
uating a texture image analysis method, a number of
aspects such as change in rotation and scale should
be considered. The performance evaluation of our
approach is implemented in the following different
cases. Based on the experiences of the authors, R = 3
is used for the radius and P = 8 pixels are used for
the sampling points in LBP operator, in which it rep-
resents the texture images well.
3.1 Rotation Invariance
For the case of rotation invariance, we test if our ap-
proach can cope with the rotation of the image change
with respect to the viewpoint.
Figure 3: Examples of texture images in (Lazebnik et al.,
2005).
We randomly select 5 unrotated and 5 rotated im-
ages from all 25 texture classes (Fig. 3) in textured
surfaces to obtain 250 images. Then the proposed
approach is applied to express these images, and the
value of recall of clustering is computed. Because the
initialization value of k-means gives influence on the
experiments, this experiment runs 5 times to obtain
the average recall. As the result, the average recall
reached to 89 percent, which is close to the results
(88.1 to 92.6 percent) obtained in (Lazebnik et al.,
2005). The average recall got by only using data
compression representation is 72 percent. This result
showed that our approach is able to deal with the case
when images changed in rotation.
Though images changed in rotation, the combi-
nation of LBP operator and data compression rep-
resentation was able to find out frequent patterns
when textures appear in images repeatedly. Hence
TEXTURE IMAGE ANALYSIS USING LBP AND DATA COMPRESSION
439
our approach may extract frequent pattern for images
changed in rotation.
3.2 Texture Image Clustering
For testing the representation performance, we also
evaluated if our approach can separate textures
from many different groups extracted from Brodatz
database (Fig. 4).
Figure 4: Examples from Brodatz database.
The Brodatz database consists of 111 images.
They are formed into classes by partitioning each im-
age into nine nonoverlapping fragments, for a total of
999 images. Fragment resolution is 213 × 213 pixels.
We randomly select 10 different textures in Bro-
datz database to get 90 images. The proposed ap-
proach is applied to separate these images. For the
same reason described previously, this experiment
runs 10 times to compute average recall. And the av-
erage recall reached to 92.6 percent. It was 83 per-
cent when only using data compression representa-
tion. Compared to the results (49.3 to 87.2 percent)
in (Ojala et al., 2002), this result showed that our
approach was applicable to represent images in Bro-
datz database. Although larger number of images in
more complicated situation were used in (Ojala et al.,
2002), the learning (or training) step is not necessary
in our proposed approach.
4 CONCLUSIONS
In this study we introduced a texture image represen-
tation method based on the combination of LBP oper-
ator and data compression, in which the training step
is not necessary. We evaluated the representation per-
formance of our approach under the consideration of
texture image changes in rotation. The experiments
were implemented with both Brodatz database and
textured surfaces. Our approach showed good perfor-
mance in the experiments. Its effectiveness shows its
potential applicability to other application of texture
image analysis. The future work includes the com-
parison with other methods using large-scale dataset.
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