Submitted to IEEE Transactions on Image Processing
1
Abstract—In this paper, a completed modeling of the LBP
operator is proposed and an associated completed LBP (CLBP)
scheme is developed for texture classification. A local region is
represented by its center pixel and a local difference
sign-magnitude transform (LDSMT). The center pixels represent
the image gray level and they are converted into a binary code,
namely CLBP-Center (CLBP_C), by global thresholding.
LDSMT decomposes the image local differences into two
complementary components: the signs and the magnitudes, and
two operators, namely CLBP-Sign (CLBP_S) and
CLBP-Magnitude (CLBP_M), are proposed to code them. The
traditional LBP is equivalent to the CLBP_S part of CLBP, and
we show that CLBP_S preserves more information of the local
structure than CLBP_M, which explains why the simple LBP
operator can extract the texture features reasonably well. By
combining CLBP_S, CLBP_M, and CLBP_C features into joint
or hybrid distributions, significant improvement can be made for
rotation invariant texture classification.
Index Terms—Local Binary Pattern, Rotation Invariance,
Texture Classification
I. INTRODUCTION
exture classification is an active research topic in computer
vision and pattern recognition. Early texture classification
methods focus on the statistical analysis of texture images. The
representative ones include the co-occurrence matrix method
[1] and the filtering based methods [2]. Kashyap and
Khotanzad [3] were among the first researchers to study
rotation-invariant texture classification by using a circular
autoregressive model. In the early stage, many models were
explored to study rotation invariance for texture classification,
including hidden Markov model [4] and Gaussian Markov
random filed [5]. Recently, Varma and Zisserman [6] proposed
to learn a rotation invariant texton dictionary from a training set,
and then classify the texture image based on its texton
distribution. Later, Varma and Zisserman [7-8] proposed
another texton based algorithm by using the image local patch
to represent features directly. Some works have been recently
proposed for scale and affine invariant texture classification by
using fractal analysis [9-10] and affine adaption [11-12].
In [13], Ojala et al proposed to use the Local Binary Pattern
(LBP) histogram for rotation invariant texture classification.
LBP is a simple yet efficient operator to describe local image
pattern, and it has achieved impressive classification results on
The work is partially supported by the GRF fund from the HKSAR
Government, the central fund from Hong Kong Polytechnic University, and the
National Science Foundation of China.
Z. Guo, L. Zhang and D. Zhang are with Department of Computing, the
Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
({cszguo, cslzhang, csdzhang}@comp.polyu.edu.hk).
* Corresponding author, phone: 852-27667271, fax: 852-27740842
representative texture databases [14]. LBP has also been
adapted to many other applications, such as face recognition
[15], dynamic texture recognition [16] and shape localization
[17].
Despite the great success of LBP in computer vision and
pattern recognition, its underlying working mechanism still
needs more investigation. Before proposing LBP, Ojala et al
[18] used the Absolute Gray Level Difference (AGLD)
between a pixel and its neighbours to generate textons, and
used the histogram of them to represent the image. Later, they
proposed LBP [13] to use the sign, instead of magnitude, of the
difference to represent the local pattern. Ojala et al [19] also
proposed a multidimensional distribution of Signed Gray Level
Difference (SGLD) and regarded LBP as a simplified operator
of SGLD by keeping sign patterns only. Ahonen and
Pietikäinen [20] analyzed LBP from a viewpoint of operator
implementation. Tan and Triggs [21] proposed Local Ternary
Pattern (LTP) to quantize the difference between a pixel and its
neighbours into three levels. Although some variants of LBP,
such as derivative-based LBP [17], dominant LBP [22] and
center-symmetric LBP [23], have been proposed recently, there
still remain some questions to be better answered for LBP. For
example, why the simple LBP code could convey so much
discriminant information of the local structure? What kind of
information is missed in LBP code, and how to effectively
represent the missing information in the LBP style so that better
texture classification can be achieved?
This paper attempts to address these questions by proposing
a new local feature extractor to generalize and complete LBP,
and we name the proposed method completed LBP (CLBP). In
CLBP, a local region is represented by its center pixel and a
local difference sign-magnitude transform (LDSMT). The
center pixel is simply coded by a binary code after global
thresholding, and the binary map is named as CLBP_Center
(CLBP_C). The LDSMT decomposes the image local structure
into two complementary components: the difference signs and
the difference magnitudes. Then two operators, CLBP-Sign
(CLBP_S) and CLBP-Magnitude (CLBP_M), are proposed to
code them. All the three code maps, CLBP_C, CLBP_S and
CLBP_M, are in binary format so that they can be readily
combined to form the final CLBP histogram. The CLBP could
achieve much better rotation invariant texture classification
results than conventional LBP based schemes.
Several observations can be made for CLBP. First, LBP is a
special case of CLBP by using only CLBP_S. Second, we will
show that the sign component preserves more image local
structural information than the magnitude component. This
explains why the simple LBP (i.e. CLBP_S) operator works
much better than CLBP_M for texture classification. Third, the
proposed CLBP_S, CLBP_M and CLBP_C code maps have
Zhenhua Guo, Lei Zhang, Member, IEEE, and David Zhang
*
, Fellow, IEEE
A Completed Modeling of Local Binary Pattern
Operator for Texture Classification
T