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Sliding-Window Designs for Vertex-Based shape coding

IEEE TRANSACTIONS ON MULTIMEDIA 2012年第3期14卷 683-692页

作者： Sohel, Ferdous A. Karmakar, Gour C. Dooley, Laurence S. Bennamoun, Mohammed Univ Western Australia Sch Comp Sci & Software Engn Crawley Australia Monash Univ Gippsland Sch Informat Technol Churchill Australia Open Univ Dept Commun & Syst Milton Keynes MK7 6AA Bucks England

Traditionally the sliding window (SW) has been employed in vertex-based operational rate distortion (ORD) optimal shape coding algorithms to ensure consistent distortion (quality) measurement and improve computational efficiency. It also regulates the memory requirements for an encoder design enabling regular, symmetrical hardware implementations. This paper presents a series of new enhancements to existing techniques for determining the best SW-length within a rate-distortion (RD) framework, and analyses the nexus between SW-length and storage for ORD hardware realizations. In addition, it presents an efficient bit-allocation strategy for managing multiple shapes together with a generalized adaptive SW scheme which integrates localized curvature information (cornerity) on contour points with a bi-directional spatial distance, to afford a superior and more pragmatic SW design compared with existing adaptive SW solutions which are based on only cornerity values. Experimental results consistently corroborate the effectiveness of these new strategies.

关键词： Image processing shape coding sliding window

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Highly efficient contour-based predictive shape coding

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PATTERN RECOGNITION LETTERS 2015年 65卷 131-136页

作者： Zhu, Zhong-jie Wang, Yu-er Jiang, Gang-yi Zhejiang Wanli Univ Ningbo Key Lab DSP Ningbo 315100 Zhejiang Peoples R China Ningbo Univ Inst Circuits & Syst Ningbo 315211 Zhejiang Peoples R China

A new scheme for contour based predictive shape coding is proposed aiming to acquire high coding efficiency, where the temporal correlations among object contours are effectively exploited. For a given binary shape image, the object contours are firstly extracted and thinned to be perfect single-pixel width followed by chain based representation. Then a chain based motion estimation and compensation technique is developed to remove temporal correlations among object contours to reduce the data to be encoded. Finally, by further exploiting the spatial correlations within chain links, a novel method is introduced to efficiently encode the residuals together with the motion displacements. Experiments are conducted and the results show that the proposed scheme is considerably more efficient than the existing techniques. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Image coding shape coding Predictive coding High efficiency

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Optimal bit allocation for joint texture-aware contour-based shape coding and shape-adaptive texture coding

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2008年第6期18卷 840-844页

作者： Bandyopadhyay, Saurav K. Kondi, Lisimachos P. W&W Comm DSP Res Sunnyvale CA 94086 USA Univ Ioannina Dept Comp Sci GR-45110 Ioannina Greece

In this paper, an operationally optimal joint shape and texture coding algorithm is proposed that uses shape-adaptive texture coding as well as texture-aware shape coding. The solution is optimal in the operational rate distortion sense, i.e, given the coding setup, the solution will guarantee the smallest possible distortion for a given rate. The shape is approximated using polygons or higher order curves. We also consider biasing the cost function to favor horizontal and vertical edges for the case of polygon approximation (biased polygon approximation). The texture is encoded using shape-adaptive discrete cosine transform. or shape-adaptive discrete wavelet transform of the MPEG-4 video codec. A comparison is drawn between the two techniques. Both a fixed-width and a variable-width tolerance band for shape coding are considered. The variable width of the tolerance band is a function of the texture profile, i.e, the width is inversely proportional to the magnitude of the image gradient. Experimental results are presented and conclusions are drawn.

关键词： optimization shape-adaptive discrete cosine transform (SA-DCT) shape-adaptive discrete wavelet transform (SA-DWT) shape coding texture coding

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Image-dependent shape coding and representation

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2005年第3期15卷 345-354页

作者： Luo, HT Hewlett Packard Labs Palo Alto CA 94304 USA

We present a new shape-coding algorithm to support object-based representation, which differs from previous algorithms in that it encodes shape as dependent meta data for image description. Therefore, both the shape-coding and decoding processes of this algorithm are designed to be dependent on the underlying image in which the object (described by the shape) is contained. This way, the correlation between image and shape is effectively removed and the shape-coding efficiency is improved on average by three times over the state-of-the-art algorithms. To facilitate comparison, a generalized "contour-generating" framework is introduced to formulate the shape-coding problem. From this framework we derive both the proposed algorithm and a number of state-of-the-art algorithms, and show that the rate-distortion (RD) criterion can be studied in a uniform way under this framework. Specifically, a dynamic-programming-based algorithm is designed to find the RD optimal coding result for the proposed algorithm. As an extension, we also discuss the complexity and scalability issues related to the application design of the proposed algorithm.

关键词： graph search object-based representation object segmentation shape coding

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A contour-based approach to binary shape coding using a multiple grid chain code

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SIGNAL PROCESSING-IMAGE COMMUNICATION 2000年第7-8期15卷 585-599页

作者： Nunes, P Marqués, F Pereira, F Gasull, A Inst Super Tecn Inst Telecomun P-1049001 Lisbon Portugal Univ Politecn Catalunya ES-08034 Barcelona Spain

This paper presents a contour-based approach to efficiently code binary shape information in the context of object-based video coding. This approach meets some of the most important requirements identified for the MPEG-4 standard, notably efficient coding and low delay. The proposed methods support both object-based lossless and quasi-lossless coding modes. For the cases where low delay is a primary requirement, a macroblock-based coding mode is proposed which can take advantage of inter-frame coding to improve the coding efficiency. The approach presented here relies on a grid different from that used for the pixels to represent the shape - the hexagonal grid - which simplifies the task of contour coding. Using this grid, an approach based on a differential chain code (DCC) is proposed for the lossless mode while, for the quasi-lossless case, an approach based on the multiple grid chain code (MGCC) principle is proposed. The MGCC combines both contour simplification and contour prediction to reduce the number of bits needed to code the shapes. Results for alpha plane coding of MPEG-4 video test sequences are presented in order to illustrate the performance of the several modes of operation, and a comparison is made with the shape-coding tool chosen by MPEG-4. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： shape coding contour coding hexagonal grid multiple grid chain code motion estimation/compensation object-based video coding

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Optimal buffered compression and coding mode selection for MPEG-4 shape coding

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IEEE TRANSACTIONS ON IMAGE PROCESSING 2001年第5期10卷 686-700页

作者： Lee, JB Cho, JS Eleftheriadis, A Columbia Univ Dept Elect Engn New York NY 10027 USA

We propose an optimal buffered compression algorithm for shape coding as defined in the forthcoming MPEG-4 international standard. The MPEG-4 shape coding scheme consists of two steps: first, distortion is introduced by down and up scaling;then, context-based arithmetic encoding is applied. Since arithmetic coding is "lossless," the down up scaling step is considered as a virtual quantizer. We first formulate the buffer-constrained adaptive quantization problem for shape coding, and then propose an algorithm for the optimal solution under buffer constraints. Recently the fact that a conversion ratio (CR) of 1/4 makes coded image irritating to human observers for QCIF size was reported for MPEG-4 shape coding. Therefore, a careful consideration for small size images such as QCIF should be given to prevent coded images from being unacceptable. To this end, a low bit rate tuned algorithm is proposed in this paper as well. Experimental results are given using an MPEG-4 shape codec.

关键词： .texture coding shape coding

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An efficient rate-distortion optimal shape coding approach utilizing a skeleton-based decomposition

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IEEE TRANSACTIONS ON IMAGE PROCESSING 2003年第10期12卷 1181-1193页

作者： Wang, HH Schuster, GM Katsaggelos, AK Pappas, TN Northwestern Univ Dept Elect & Comp Engn Evanston IL 60208 USA Hsch Tech Abt Elektrotech CH-8040 Rapperswil Switzerland

In this paper, we present a new shape-coding approach, which decouples the shape information into two independent signal data sets;the skeleton and the boundary distance from the skeleton. The major benefit of this approach is that it allows for a more flexible tradeoff between approximation error and bit budget. Curves of arbitrary order can be utilized for approximating both the skeleton and distance signals. For a given bit budget for a video frame, we solve the problem of choosing the number and location of the control points for all skeleton and distance signals of all boundaries within a frame, so that the overall distortion is minimized. An operational rate-distortion (ORD) optimal approach using Lagrangian relaxation and a four-dimensional Direct Acyclic Graph (DAG) shortest path algorithm is developed for solving the problem. To reduce the computational complexity from O(N-5) to O(N-3), where N is the number of admissible control points for a skeleton, a suboptimal greedy-trellis search algorithm is proposed and compared with the optimal algorithm. In addition, an even more efficient algorithm with computational complexity O(N-2) that finds an ORD optimal solution using a relaxed distortion criterion is also proposed and compared with the optimal solution. Experimental results demonstrate that our proposed approaches outperform existing ORD optimal approaches, which do not follow the same decomposition of the source data.

关键词： boundary coding object-based video compression rate-distortion optimization shape coding skeleton decomposition skeletonization

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A new adaptive vertex-based binary shape coding technique

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IMAGE AND VISION COMPUTING 2007年第6期25卷 863-872页

作者： Kuo, Chung-Ming Hsieh, Chaur-Heh Huang, Yong-Ren I Shou Univ Dept Informat Engn Kaohsiung 840 Taiwan Shu Te Univ Dept Informat Engn Kaohsiung 824 Taiwan

This paper presents a new adaptive vertex-based coding scheme to improve the coding efficiency of the object shapes of a video sequence. We first smooth out the original contour using the property of perfect 8-connectivity, which reduces the number of vertexes without loss of quality. Then we propose top-down and bottom-up algorithms to select the vertex points. In the top-down scheme, we develop a new adjusting technique to measure the distortion. It is simple for both calculation and implementation, and the reconstructed shape has better quality. In the bottom-up scheme, we develop a new area-based measure that makes the insertion of a new vertex easy. Finally, we propose a scheme that employs multiple dynamic ranges to modify the object-adaptive vertex coding method. It improves the coding performance significantly. (C) 2006 Elsevier B.V. All rights reserved.

关键词： shape coding vertex-based coding modified object-adaptive vertex encoding

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Hybrid scheme for efficient shape coding

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DIGITAL SIGNAL PROCESSING 2014年 30卷 131-140页

作者： Zhu, Zhongjie Jiang, Gangyi Zhejiang Wanli Univ Ningbo Key Lab DSP Ningbo 315100 Zhejiang Peoples R China Ningbo Univ Inst Circuits & Syst Ningbo 315211 Zhejiang Peoples R China

A contour-based scheme for near lossless shape coding is proposed aiming to acquire high coding efficiency. For a given shape image, object contours are firstly extracted and then thinned to be perfect single-pixel width. Next they are transformed into chain-based representation and divided into different chain segments based on link directions. Thirdly, two fundamental coding modes are designed and developed to encode different types of chain segments, where the spatial correlations within object contours are analyzed and exploited to improve the coding efficiency as high as possible. Finally, a fast and efficient mode selection method is introduced to select the one that can produce shorter code length out of the two modes for each chain segment. Experiments are conducted and the results show that the proposed scheme is considerably more efficient than the existing techniques. (C) 2014 Elsevier Inc. All rights reserved.

关键词： shape coding Contour-based coding Near lossless coding Hybrid scheme High efficiency

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Graph convolutional autoencoder model for the shape coding and cognition of buildings in maps

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INTERNATIONAL JOURNAL OF GEOGRAPHICAL INFORMATION SCIENCE 2021年第3期35卷 490-512页

作者： Yan, Xiongfeng Ai, Tinghua Yang, Min Tong, Xiaohua Tongji Univ Coll Surveying & Geoinformat Shanghai Peoples R China Wuhan Univ Sch Resource & Environm Sci Wuhan Peoples R China

The shape of a geospatial object is an important characteristic and a significant factor in spatial cognition. Existing shape representation methods for vector-structured objects in the map space are mainly based on geometric and statistical measures. Considering that shape is complicated and cognitively related, this study develops a learning strategy to combine multiple features extracted from its boundary and obtain a reasonable shape representation. Taking building data as example, this study first models the shape of a building using a graph structure and extracts multiple features for each vertex based on the local and regional structures. A graph convolutional autoencoder (GCAE) model comprising graph convolution and autoencoder architecture is proposed to analyze the modeled graph and realize shape coding through unsupervised learning. Experiments show that the GCAE model can produce a cognitively compliant shape coding, with the ability to distinguish different shapes. It outperforms existing methods in terms of similarity measurements. Furthermore, the shape coding is experimentally proven to be effective in representing the local and global characteristics of building shape in application scenarios such as shape retrieval and matching.

关键词： shape coding graph convolutional autoencoder (GCAE) spatial cognition deep learning vector building data

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