EVALUATING THE POTENTIAL OF TEXTURE AND COLOR
DESCRIPTORS FOR REMOTE SENSING IMAGE RETRIEVAL AND
CLASSIFICATION
Jefersson A. dos Santos, Ot´avio A. B. Penatti and Ricardo da S. Torres
RECOD Lab / LIS, Institute of Computing, University of Campinas – Unicamp, 13084–970, Campinas, SP, Brazil
Keywords:
Image descriptors, Remote sensing image, Image classification, Image retrieval.
Abstract:
Classifying Remote Sensing Images (RSI) is a hard task. There are automatic approaches whose results nor-
mally need to be revised. The identification and polygon extraction tasks usually rely on applying classification
strategies that exploit visual aspects related to spectral and texture patterns identified in RSI regions. There
are a lot of image descriptors proposed in the literature for content-based image retrieval purposes that may be
useful for RSI classification. This paper presents a comparative study to evaluate the potential of using suc-
cessful color and texture image descriptors for remote sensing retrieval and classification. Seven descriptors
that encode texture information and twelve color descriptors that can be used to encode spectral information
were selected. We perform experiments to evaluate the effectiveness of these descriptors, considering image
retrieval and classification tasks. To evaluate descriptors in classification tasks, we also propose a methodology
based on KNN classifier. Experiments demonstrate that Joint Auto-Correlogram (JAC), Color Bitmap, Invari-
ant Steerable Pyramid Decomposition (SID) and Quantized Compound Change Histogram (QCCH) yield the
best results.
1 INTRODUCTION
Agriculture has an important role in the economy of
several countries. The results of agricultural activi-
ties are directly linked to the productivity. Therefore,
many researches have been investigating new ways to
improve agricultural practices and, consequently, to
increase the quantity and quality of what is produced.
In this scenario, crop monitoring is a fundamental
activity and using Geographic Information Systems
(GIS) has made it easier.
Some of the main issues related to crop monitor-
ing are: How is the land occupation? What is cul-
tivated in a given region? Where are some cultures
cultivated?
Remote Sensing Images (RSIs) provide the ba-
sis for the creation of information systems that sup-
port the decision-making process based on land cover
changes. Using RSI in crop monitoring requires the
recognition of the regions of interest and the extrac-
tion of the polygons around these regions.
The identification and polygon extraction tasks
usually rely on applying classification strategies that
exploit visual aspects related to spectral and texture
patterns identified in RSI regions. These tasks can
be performed automatically or manually. The “man-
ual” approach is based on image editors by witch
users can define or draw polygons that represent re-
gions of interest using the raster image as back-
ground. In general, automatic approaches use clas-
sification strategies based on pixel information. How-
ever, the most used pixel classification algorithm,
MaxVer (Showengerdt, 1983) is not always effective.
The main drawback of automatic approaches is
concerned with its sensitivity to image noises (e.g.,
for example, distortions that can be found in moun-
tainous regions). Another important problem in the
automatic approaches is concerned with the fact that
they usually fail to correctly identify borders between
distinct regions within the same image. Thus, in prac-
tical situations, the results obtained need to be revised.
As these revisions take a lot of time, it is sometimes
more convenient to the user to perform recognition
manually.
Content-based Image Retrieval (CBIR) systems
are developed to provide efficient and effective means
to retrieve images. In these systems, the searching
process consists of, for a given image, computing the
most similar images stored in the database, consider-
ing only image properties, like color and texture, for
203
A. dos Santos J., A. B. Penatti O. and da S. Torres R. (2010).
EVALUATING THE POTENTIAL OF TEXTURE AND COLOR DESCRIPTORS FOR REMOTE SENSING IMAGE RETRIEVAL AND CLASSIFICATION.
In Proceedings of the International Conference on Computer Vision Theory and Applications, pages 203-208
DOI: 10.5220/0002843402030208
Copyright
c
SciTePress
instance. The searching process relies on the use of
image descriptors. A descriptor can be characterized
by two functions: feature vector extraction and sim-
ilarity computation. The similarity between two im-
ages is computed as a function of their feature vectors
distance.
This paper presents an evaluation of image de-
scriptors for RSI retrieval and classification. Seven
descriptors that encode texture information and
twelve color descriptors that can be used to encode
spectral information were selected. We perform ex-
periments to evaluate the effectiveness of these de-
scriptors in retrieval sessions and classification tasks.
2 RELATED WORK
Several methods have been proposed to improve the
performance of RSI classification techniques. In (Mo
et al., 2007), a new method considering image seg-
mentation, GIS, and data mining algorithms was pre-
sented. Compared with pixel-based classification, the
results showed best agreement with visual interpre-
tation. The work proposed in (Yildirim et al., 2005)
applied a morphological filter in an image which was
classified by MaxVer algorithm. The results were
compared with the other classification algorithms
(Fisher linear likelihood, minimum Euclidean dis-
tance and ECHO). In (hyung Kim et al., 2007), three
Land Cover Classification Algorithms are compared
for monitoring North Korea using multi-temporal
data.
Recently, some descriptors for RSI purposes have
been proposed. Tusk et. al. (Tusk et al., 2003) pre-
sented algorithms that allow automatic selection of
features for region and tile similarity searches apply-
ing relevance feedback. Samal et. al. (Samal et al.,
2009) proposed a RSI descriptor, called SIMR (Satel-
lite Image Matching and Retrieval). SIMR computes
spectral and spatial attributes of the images using a
hierarchical representation. A unique aspect of this
descriptor are the couples of second-level spatial au-
tocorrelation with quad tree structure.
There is a large number of image descriptors pro-
posed in the literature for CBIR that can be useful
to classify and recognize RSI regions. Using de-
scriptors, systems can compute how similar regions
of an image are when compared to a spectral or tex-
ture pattern in which users are interested. This infor-
mation can, therefore, be used to classify the whole
image. Santos et. al. (dos Santos et al., 2009) pre-
sented a semi-automatic method to vectorize regions
from remote sensing images using relevance feedback
based on genetic programming (GP). The solution
consists of using image descriptors to encode texture
and spectral features from the images, applying rel-
evance feedback based on GP to combine these fea-
tures with information obtained from the users inter-
actions and, finally, segment the image. At the end,
segmented image (raster) is converted into a vector
representation.
Descriptors effectiveness can vary from one ap-
plication to another. This fact shows the importance
of evaluating descriptors considering specific appli-
cations. A comparative study of color descriptors for
Web image retrieval is presented in (Penatti and Tor-
res, 2008). However, to the best of our knowledge no
study has been conducted to evaluate the performance
and effectiveness of image descriptors in RSI retrieval
and classification tasks.
3 IMAGE DESCRIPTORS
The descriptors chosen for the evaluation are impor-
tant descriptors from the literature and recently pro-
posed descriptors.
The color descriptors evaluated in this work are:
GCH (Swain and Ballard, 1991), CGCH (Stricker
and Orengo, 1995), LCH (Swain and Ballard, 1991),
CCV (Pass et al., 1996), ACC (Huang et al., 1997),
JAC (Williams and Yoon, 2007), BIC (de O. Stehling
et al., 2002), CBC (de O. Stehling et al., 2001),
Color Bitmap (Lu and Chang, 2007), CSD (Man-
junath et al., 2001), CW-HSV (Utenpattanant et al.,
2006) and CM (Paschos et al., 2003).
The texture descriptors evaluated in this work are:
LBP (Ojala et al., 2002), HTD (Wu et al., 2000),
SID (Zegarra et al., 2007), CCOM (Kovalev and
Volmer, 1998), Unser (Unser, 1986), QCCH (Huang
and Liu, 2007), and LAS (Tao and Dickinson, 2000).
4 EXPERIMENTS
This section presents the databases used in the exper-
iments and the measures used to evaluate the descrip-
tors.
4.1 Image Databases
Two image databases were created to evaluate image
descriptors based on distinct RSIs. One of them can
be classified as “easy recognition” (pasture image)
while the other as “hard recognition” (coffee image).
Information about the used RSIs is showed in Table 1.
In the experiments, one image is represented by a
tile from the original RSI. The size of the tile was
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Table 1: Remote Sensing Images used in the experiments.
Image1 Image2
Region of interest pasture coffee
Terrain plain mountainous
Satelite CBERS SPOT
Spatial resolution 20 meters 2,5 meters
Bands composition R-IR-G (342) IR-NIR-R (342)
Acquisition date 08–20–2005 08–29–2005
Location Laranja Azeda Monte Santo
Basin, MS County, MG
Dimensions (px) 1310× 1842 2400× 2400
fixed according to the common extension value of
a region of interest. Coffee crops are normally in
small parcels on the same farm. We defined that
75 × 75 meters is a good value to the size of the
partition. For pasture parcels, that are larger, the
chosen value was 400 × 400 meters. The dimen-
sion of partitions are fixed in the experiments. We
used 30× 30 pixels to partition the coffee image and
20 × 20 pixels for the pasture image. The number of
partitions for the pasture and coffee images was 5980
and 6400, respectively.
A “mask” containing all regions of interest from
the RSIs used in the experiments was used to know
the class of each tile. A “mask” is a binary image
where value 1 represents pixels of regions of interest.
The “masks” used in our experiments were classified
manually by agricultural specialists.
4.2 Evaluation Measures
The main objective of the experiments was to evaluate
and compare the descriptors considering effectiveness
issues. For this purpose, we configured two experi-
ments: retrieval effectiveness evaluation and overall
accuracy classification.
To evaluate retrieval effectiveness, Precision ×
Recall curves were used. Precision quantifies the per-
centage of relevant images present in the retrieved
results. Recall is a measure that represents the per-
centage of the relevant images that are retrieved. A
Precision × Recall curve indicates the variation in
Precision values as the rate of relevant images from
the database (Recall) changes. Intuitively, the higher
the curve, the better the effectiveness. The Precision
and Recall curves were computed based on the av-
erage values obtained for each query image in each
database. We used 340 and 100 queries in the Pasture
and Coffee image sets respectively for all the color
and texture descriptors presented in Section 3.
To compute the overall accuracy of each descrip-
tor we implemented a variation of K-Nearest Neigh-
boor (KNN) classifier. First of all, a set of tiles
from the database was randomly selected to be used
as training set. The set, corresponding to 10% of
the database size, is composed by relevants and non-
relevants samples in the same proportion found in the
full database. To classify one tile, each descriptor
evaluated was used to compute the distance between
the given tile and all the training set tiles. Based on
the descriptor distances, the training set is ranked and
the first K tiles are weighted inversely proportional
to their position in the rank. Finally, the sum of the
tiles’ weights for each class (relevant or non-relevant)
is computed. The greater sum indicates the class of
the input tile. To test the classification effectiveness
of the descriptors 100 tiles were used for each RSI.
4.3 Results
Figures 1, 2, 3, and 4 show the Precision × Re-
call curves for color and texture descriptors in the
databases used.
From Figure 1 we can see that good descrip-
tors considering retrieval effectiveness are JAC, Color
Bitmap, and ACC.
0
0.2
0.4
0.6
0.8
1
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Precision
Recall
ACC
BIC
CBC
CCV
CGCH
CM
CSD
CW-HSV
GCH
JAC
LCH
Color Bitmap
Figure 1: Precision × Recall curves for color descriptors in
the Pasture Image Set.
From Figure 2, it is possible to see that JAC
presents the highest Precision values even for small
values of Recall and for Recall equal to 1.
Analyzing Figure 3 it is possible to notice that SID
has the highest Precision values for all values of Re-
call.
Considering curves for the Coffee database in Fig-
ure 4, it is possible to see that the descriptors present
very similar Precision valuesand these values are near
32% when Recall reaches 10%.
After analyzing the curves for color and texture
descriptors it is possible to say that color descrip-
tors are slightly better than texture descriptors for the
databases used. For example, in the Pasture database,
for Recall equal to 10%, the highest Precision value
for color descriptors is around 62% (JAC) and for
EVALUATING THE POTENTIAL OF TEXTURE AND COLOR DESCRIPTORS FOR REMOTE SENSING IMAGE
RETRIEVAL AND CLASSIFICATION
205
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Precision
Recall
ACC
BIC
CBC
CCV
CGCH
CM
CSD
CW-HSV
GCH
JAC
LCH
Color Bitmap
Figure 2: Precision × Recall curves for color descriptors in
the Coffee Image Set.
0
0.2
0.4
0.6
0.8
1
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Precision
Recall
CCOM
HTD
LAS
LBP
QCCH
SID
Unser
Figure 3: Precision × Recall curves for texture descriptors
in the Pasture Image Set.
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Precision
Recall
CCOM
HTD
LAS
LBP
QCCH
SID
Unser
Figure 4: Precision × Recall curves for texture descriptors
in the Coffee Image Set.
texture descriptors is near 47%. For Recall equal to
1, color descriptors achieve Precision of 25% (Color
Bitmap) and texture descriptors achieve almost 23% .
For the Coffee database, it is possible to notice that,
for Recall equal to 10%, the highest curve of a color
descriptor reaches 61% (JAC) while the highest curve
of a texture descriptor reaches almost 40% (SID). For
Recall equal to 1, there is almost no difference in the
Precision values.
According to the results for the coffee database
presented (Figure 5), is observed that some descrip-
tors achieved high overall accuracy values. The color
descriptors BIC, ACC, CBC, Color Bitmap, and JAC
were the best ones reaching more than 60% of overall
accuracy for any k. JAC produced the highest accu-
racy values, being the only one with values over 70%
(72% for k=1, 79% for k=3, and 73% for k=7 and
k=10). With regard to the texture descriptors, QCCH,
SID, and LAS yielded the highest accuracy values,
52% for k=3. For k values different than 3, the tex-
ture descriptors presented accuracy below 48%. The
CCOM descriptor did not reach 25% of accuracy in
any of the experiments in the coffee database.
According to the results for the pasture database
presented (Figure 6) we can see that some descrip-
tors yielded good accuracy values. The color descrip-
tors JAC, Color Bitmap, and CBC reached near or
more than 60% of overall accuracy. JAC descriptor
was again the descriptor with highest accuracy value,
reaching 78% for k=3 and being over 65% for all k
values. The texture descriptors yielded lower accu-
racy values when compared with most of color de-
scriptors. QCCH, SID and Unser were the only tex-
ture descriptors to reach accuracy above 50%. For
k=3, QCCH reached 58% of accuracy, SID 55% and
Unser 53%. CCOM descriptor reached the lowest ac-
curacy values, being below 25% for all k values.
Considering the accuracy values in both image
databases, we can point JAC as the best color de-
scriptor. However, JAC generates big feature vec-
tors and so, it is slower to compare them. If storage
and time requirements are not critical, JAC is the best
choice. Other descriptors with near effectiveness are
CBC and Color Bitmap. CBC has complex extraction
and distance function. Color Bitmap is the best choice
among the color descriptors, which balance simple al-
gorithms and good effectiveness. Amongst the texture
descriptors, QCCH and SID reached the highest ac-
curacy values, being SID computationally more com-
plex than QCCH for features extraction.
5 CONCLUSIONS
This paper presents a comparative study of image de-
scriptors for the classification and recognition of RSI
regions. Twelve color descriptors and seven texture
descriptors were compared considering effectiveness
issues. The effectiveness was measured by precision-
recall curves and overal accuracy. JAC and Color
Bitmap presented the best results among the color de-
scriptors evaluated, while SID was the best texture de-
scriptor. We also proposed methodology to evaluate
VISAPP 2010 - International Conference on Computer Vision Theory and Applications
206
Figure 5: Overall accuracy classification of each descriptor for Coffee using KNN 1, 3, 7 and 10.
Figure 6: Overall accuracy classification of each descriptor for Pasture KNN 1, 3, 7 and 10.
image descriptors in classification problems by using
KNN classifier.
The next stage of this work is to combine the best
descriptors and to evaluate their use in RSI classifica-
tion tasks.
ACKNOWLEDGEMENTS
Authors thank to FAPESP, CNPq (BioCORE project)
and Fapesp-Microsoft Research Virtual Institute
(eFarms project) for financial support.
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