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CORNER DETECTION FOR chain CODED CURVES

PATTERN RECOGNITION 1995年第6期28卷 843-852页

作者： KOPLOWITZ, J PLANTE, S TRW CO INC NEW LONDONCT 06320

A corner detection scheme for chain coded curves is proposed that significantly improves on the performance of current algorithms. The proposed scheme measures the number of links to either side of a point that can produce the largest digital straight line. That value is used as an indication of curvature at that point with very high curvature being indicative of a corner. A modification of the proposed algorithm can further reduce the false detection rate with virtually no affect on the number of corners missed by omitting certain patterns that can arise from contours with arbitrarily small curvature.

关键词： chain coding CORNER DETECTION LINE DRAWINGS IMAGE ANALYSIS DIGITIZED IMAGES BINARY IMAGES FEATURE EXTRACTION

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Partitions: A taxonomy of types and representations and an overview of coding techniques

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SIGNAL PROCESSING-IMAGE COMMUNICATION 1997年第1-3期10卷 5-19页

作者： deSequeira, MM Cortez, D Torre Norte 10–15 Instituto de Telecomunicações IST 1096 Lisboa Cedex Portugal

Recognising the importance of partition or shape coding in the field of image and video coding, and the fact that a systematisation of the subject would simplify the comparison of partition coding techniques, this paper proposes a classification of partition types and partition representations into a taxonomy tree. The partition type level of the tree classifies the possible partition types that may have to be coded. The partition representation level classifies the possible representations for each partition type. This paper also overviews the partition coding techniques which address the considered partition types and which use the identified partition representations. Emphasis is given to binary partition coding techniques proposed within the framework of NIPEG-4. (C) 1997 Elsevier Science B.V.

关键词： segmentation partition coding image coding chain coding

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Information extraction from topographic map using colour and shape analysis

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SADHANA-ACADEMY PROCEEDINGS IN ENGINEERING SCIENCES 2014年第5期39卷 1095-1117页

作者： Ganpatrao, Nikam Gitanjali Ghosh, Jayanta Kumar Indian Inst Technol Dept Civil Engn Geomat Engn Grp Roorkee 247667 Uttar Pradesh India

The work presented in this paper is related to symbols and toponym understanding with application to scanned Indian topographic maps. The proposed algorithm deals with colour layer separation of enhanced topographic map using k-means colour segmentation followed by outline detection and chaining, respectively. Outline detection is performed through linear filtering using canny edge detector. Outline is then encoded in a Freeman way, the x-y offsets have been used to obtain a complex representation of outlines. Final matching of shapes is done by computing Fourier descriptors from the chain-codes;comparison of descriptors having same colour index is embedded in a normalized scalar product of descriptors. As this matching process is not rotation invariant (starting point selection), an interrelation function has been proposed to make the method shifting invariant. The recognition rates of symbols, letters and numbers are 84.68, 91.73 and 92.19%, respectively. The core contribution is dedicated to a shape analysis method based on contouring and Fourier descriptors. To improve recognition rate, obtaining most optimal segmentation solution for complex topographic map will be the future scope of work.

关键词： Colour segmentation shape analysis outline detection chain coding template matching

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Efficiency of chain codes to represent binary objects

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PATTERN RECOGNITION 2007年第6期40卷 1660-1674页

作者： Sanchez-Cruz, Hermilo Bribiesca, Ernesto Rodriguez-Dagnino, Ramon M. Univ Autonoma Aguascalientes Ctr Ciencias Basicas Dept Elect Syst Aguascalientes 20100 Ags Mexico Univ Nacl Autonoma Mexico Dept Comp Sci Inst Invest Matemat Aplicadas & Sist Mexico City 01000 DF Mexico Inst Tecnol & Estudios Super Monterrey Elect & Telecommun Ctr Monterrey 64849 NL Mexico

We present a study of compression efficiency for binary objects or bi-level images for different chain-code schemes. chain-code techniques are used for compression of bi-level images because they preserve information and allow a considerable data reduction. Furthermore, chain codes are the standard input format for numerous shape-analysis algorithms. In this work we apply chain codes to represent object with holes and we compare their compression efficiency for seven chain codes. We have also compared all these chain codes with the JBIG standard for bi-level images. (c) 2006 Pattern Recognition Society. Published by Elsevier Ltd. All rights reserved.

关键词： chain coding shapes bi-level images Huffman algorithm entropy

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A new chain code

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PATTERN RECOGNITION 1999年第2期32卷 235-251页

作者： Bribiesca, E Univ Nacl Autonoma Mexico Inst Invest Matemat Aplicadas & Sistemas Dept Comp Sci Mexico City 01000 DF Mexico

A new chain code for shapes composed of regular cells is defined. This boundary chain code is based on the numbers of cell vertices which are in touch with the bounding contour of the shape. This boundary chain code is termed cei res chain code (VCC). The VCC is invariant under translation and rotation. Also, it may be starting point normalized and invariant under mirroring transformation. Using this concept of chain code it is possible to relate the chain length to the contact perimeter, which corresponds to the sum of the boundaries of neighboring cells of the shape (Bribiesca, E., Comp. Math. Appl. 33(11) (1997) 1-9);also, to relate the chain nodes to the contact vertices, which correspond to the vertices of neighboring cells. So, in this way, these relations among the chain and the characteristics of interior of the shape allow us to obtain interesting properties. This work is motivated by the idea of obtaining various shape features computed directly from the VCC without going to Cartesian-coordinate representation. Finally, in order to illustrate the capabilities of the VCC: we present some results using real shapes. (C) 1999 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.

关键词： chain coding vertex chain code contact perimeter contact vertices shapes

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Accurate object recognition in the underwater images using learning algorithms and texture features

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MULTIMEDIA TOOLS AND APPLICATIONS 2017年第24期76卷 25679-25695页

作者： Srividhya, K. Ramya, M. M. Hindustan Inst Technol & Sci Ctr Automat & Robot Chennai 603103 Tamil Nadu India

Underwater image processing is very challenging due to its environmental conditions and poor sunlight. Images captured from the ocean using autonomous vehicles are often non-uniformly illuminated and contain noise due to the underlying environment. Object recognition is a challenging task under water due to the variation in the environment, target shape and orientation. Traditional algorithms based on spatial information may not lead to accurate segmentation as the intensity variation is often less in underwater images. Texture information representing the characteristics of the object is needed. Statistical features like autocorrelation, sum average, sum variance and sum entropy were extracted. These were fed as input to learning algorithms and training was done to effectively classify the object of interest and background. chain coding was further applied for object recognition. The proposed methodology achieved a maximum classification accuracy of 96%.

关键词： Underwater object recognition Image segmentation chain coding Back propagation neural network Texture parameters Deep learning Morphological operators

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Study of compression efficiency for three-dimensional discrete curves

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OPTICAL ENGINEERING 2008年第7期47卷 077206-1-077206-9页

作者： Sanchez-Cruz, Hermilo Bribiesca, Ernesto Univ Nacl Autonoma Mexico Dept Ciencias Computac Inst Invest Matemat Aplicadas & Sistemas Mexico City 01000 DF Mexico Autonomous Univ Mexico Mexico City DF Mexico Univ Nacl Autonoma Mexico Inst Appl Math & Syst Mexico City DF Mexico

A study of compression efficiency of 3-D chain codes to represent discrete curves is described. The 3-D Freeman chain code and the five orthogonal change chain directions (5OT) chain code are compared. The 3-D Freeman chain code consists of 26 directions, in 3-D Euclidean space, with no invariance under rotation. The 5OT chain elements represent the orthogonal direction changes of the contiguous straight-line segments of the discrete curve. This chain code only considers relative direction changes, which allows us to have a curve descriptor invariant under rotation, and mirroring curves may be obtained with ease. In the 2-D domain, Freeman chain codes are widely used to represent contour curves. Until now, the authors have had no information of implementing Freeman chain codes to compress 3-D curves. Our contribution is how to implement the Freeeman chain code in 3-D and how to compare it with the recently proposed 5OT code. Finally, to probe our results, we apply the proposed method to three different cases: arbitrary curves, cube-filling Hilbert curves, and lattice knots. (C) 2008 Society of Photo-Optical Instrumentation Engineers.

关键词： three-dimensional discrete curves chain coding entropy compression Huffman algorithm

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SKETCH BASED coding OF GREY LEVEL IMAGES

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SIGNAL PROCESSING 1988年第1期15卷 57-83页

作者： CARLSSON, S Telecommunication Theory Royal Institute of Technology S-100 44 Stockholm Sweden

We present an algorithm for data compression of grey level images based on coding geometric and grey level information of the contours in the image. From this sketch information alone an intelligible grey level image can be reconstructed. Compression ratios will be dependent on the amount of detail in the image and the quality of the reconstruction. For a human face image we present results with compression ratio in the range 60–75, with an intelligible reconstructed image. The reconstructed image lacks texture information however. This is therefore coded separately by taking the residual between the original and the sketch reconstructed image and using the Laplacian pyramid coding algorithm. The pyramid coding seems to be a natural complement to the sketch coding algorithm since the resolution of the texture to be added can be varied easily by just adding certain levels of the pyramid coded residual. Compared to traditional wave form coding the use of sketch coding only, seems to be advantageous mainly at high compression ratios in the range 30–75 giving intelligible reconstructed images. For lower compression ratios and high quality reconstructions the advantages are correspondingly less. Using sketch coding and residual pyramid coding gives visible improvement over a larger range of compression ratios compared to pyramid coding only. The main factor that limits the full exploitation of the possibilities of a sketch based coding algorithm seems to be the extraction of the perceptually essential sketch information. If this can be achieved in a more effective way the advantages compared to wave form coding will certainly increase. Zusammenfassung Ein Algorithmus zur Datenkompression für Graustufenbilder wird vorgestellt. Er beruht auf der Kodierung von Geometrie- und Graustufen-Information der Bildkonturen. Aus dieser “Skizzen-Information” allein kann ein erkennbares Graustufenbild rekonstruiert werden. Die Kompressionsfaktoren hängen ab von der Feinheit der Bilddet

关键词： Image coding edge detection contour extraction chain coding image reconstruction visual perception

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2D tree object representation via the slope chain code

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PATTERN RECOGNITION 2014年第10期47卷 3242-3253页

作者： Bribiesca, Ernesto Bribiesca-Contreras, Guadalupe Univ Nacl Autonoma Mexico Inst Invest Matemat Aplicadas & Sistemas Dept Ciencias Computac Mexico City 01000 DF Mexico Univ Nacl Autonoma Mexico Inst Ciendas Mar & Limnol Lab Sistemat & Ecol Equinodermos Mexico City 01000 DF Mexico

A method for representing 2D (two-dimensional) tree objects is described. This representation is based on a chain code, which is called the Slope chain Code (SCC). Thus, 2D tree objects are described by means of a chain of element strings suitably combined by means of parentheses. These 2D tree objects correspond to naturally existing 2D tree structures. This tree notation preserves the shape of trees (and the shape of their branches), allows us to know their topological and geometrical properties. The proposed notation of 2D tree objects is invariant under translation, rotation and, optionally, under scaling. Also, it is possible to define a unique start vertex for each tree via the unique path in the tree. Using this notation it is possible to obtain the mirror image of any tree with ease. Furthermore, two interesting properties of trees are presented: the accumulated slope and the tortuosity. Tortuosity is a very important property of trees and has many applications in different fields. In order to prove our method for representing 2D tree objects, we obtain some tree descriptors of tree objects and compute their measures of accumulated slope and tortuosity. Finally, we present some examples of 2D trees from the real world about echinoderm species identification. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： 2D tree objects 2D tree structures Tree descriptor Slope chain code chain coding 2D tree representation Measure of tortuosity

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Symmetry detection in 3D chain coded discrete curves and trees

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PATTERN RECOGNITION 2015年第4期48卷 1420-1439页

作者： Aguilar, Wendy Bribiesca, Ernesto Univ Nacl Autonoma Mexico Dept Comp Sci Inst Invest Matemat Aplicadas & Sistemas Mexico City 01000 DF Mexico

Symmetry detection in 2D and 3D shapes has been a classical problem in computer vision, computational geometry, and pattern recognition. One of the reasons of this interest, is because symmetry is related to the balance and harmony, and in most cases it is considered like a beautiful proportion. In this paper we present different methods to detect mirror and rotational symmetries in 2D and 3D open and closed curves, and in trees represented by means of the orthogonal direction change chain code. These methods detect both global and local symmetries. They can also detect the number and position of the axes of symmetry. They are simple, easy to implement and fast to execute. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Shape-of-curve symmetry 3D discrete curves 3D discrete trees chain coding Mirror symmetry detection Rotational symmetry detection

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