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Optimal constrained multi-degree reduction of Bézier curves with explicit expressions based on divide and conquer

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第4期10卷 577-582页

作者： Lian ZHOU Guo-jin WANG Institute of Computer Graphics and Image Processing State Key Lab of CAD & CG Zhejiang University Hangzhou 310027 China

We decompose the problem of the optimal multi-degree reduction of Bézier curves with corners constraint into two simpler subproblems, namely making high order interpolations at the two endpoints without degree reduction, and doing optimal degree reduction without making high order interpolations at the two endpoints. Further, we convert the second subproblem into multi-degree reduction of Jacobi polynomials. Then, we can easily derive the optimal solution using orthonormality of Jacobi polynomials and the least square method of unequally accurate measurement. This method of 'divide and conquer' has several advantages including maintaining high continuity at the two endpoints of the curve, doing multi-degree reduction only once, using explicit approximation expressions, estimating error in advance, low time cost, and high precision. More importantly, it is not only deduced simply and directly, but also can be easily extended to the degree reduction of surfaces. Finally, we present two examples to demonstrate the effectiveness of our algorithm.

关键词： Bezier curves Multi-degree reduction Divide and conquer

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A new method in highway route design:joining circular arcs by a single C-Bézier curve with shape parameter

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第4期10卷 562-569页

作者： Hua-hui CAI Guo-jin WANG Institute of Computer Graphics and Image Processing State Key Lab of CAD & CG Zhejiang University Hangzhou 310027 China

We constructed a single C-Bezier curve with a shape parameter for G^2 joining two circular arcs. It was shown that an S-shaped transition curve, which is able to manage a broader scope about two circle radii than the Bezier curves, has no curvature extrema, while a C-shaped transition curve has a single curvature extremum. Regarding the two kinds of curves, specific algorithms were presented in detail, strict mathematical proofs were given, and the effectiveness of the method was shown by examples This method has the following three advantages：（1） the pattern is unified; （2） the parameter able to adjust the shape of the transition curve is available; （3） the transition curve is only a single segment, and the algorithm can be formulated as a low order equation to be solved for its positive root. These advantages make the method simple and easy to implement.

关键词： Transition curve C-Bezier curve Monotone curvature Shape parameter

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A robust color image watermarking scheme

A robust color image watermarking scheme

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IASTED International Conference on Visualization, Imaging and image processing, VIIP 2012

作者： Wahedul Islam, Md. Alzahir, Saif Computer Science Department Image Processing and Graphics Lab UNBC BC Canada

ISBN: (纸本)9780889869264

In this paper, we present an image watermarking scheme based on discrete wavelet transform and singular value decomposition (SVD) for color images. This scheme embeds the watermark into the luminance (Y) channel of YC bCR color space of the host image. The luminance image is decomposed up to four DWT levels. SVD is applied on the HL1-4 and LH1-4sub-bands of each level and pseudo random number (PRN) sequence is added to the singular values of their coefficients to produce what we call modified singular values. To obtain the modified HL and LH coefficients, we take the inverse of the SVD of the modified SVs. Finally, we perform the IDWT on the modified HL & LH coefficients as well as HH and LL coefficients to produce the watermarked Y channel image. Then, the modified luminance, Cb and Cr are combined to get the watermarked color image. Simulation results show that our watermark is robust against high JPEG compression, filtering, Gaussian-noise, resizing and other image processing attacks. In addition, this watermark is not susceptible to any false positive or detection of false reference watermark.

关键词： image watermarking

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Towards a global Code of Ethics for engineers

Towards a global Code of Ethics for engineers

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IEEE International Symposium on Ethics in Science, Technology and Engineering

作者： Saif alZahir Laura Kombo Image Processing Graphics Lab Columbia CANADA

Theoretically, Codes of Ethics are broad guidelines to professional conduct. These codes are designed to help professionals uphold the highest level of ethical conduct and maintain standards of practice and integrity pertaining to their professional duties. Generally, these guidelines include but not limited to protecting the public interest, demonstrating professional competence, preserving confidentiality, attending to conflict of interest and perpetuating social responsibility. Although different professional engineering societies, in different counties, have different codes of ethics, but they all have some common basic teachings of right and wrong and how to apply it in decisions making process. In this paper, we examine the compatibility of the IEEE code of ethics with thirty two 32 international codes of ethics of professional engineering societies in Africa, Asia, Australia, Europe and Latin America. Our research results show that only four countries have adopted the IEEE code of ethics as is, while the other 28 countries have some variations of it i.e., adopted some articles, ignored some articles and added some of their own. Examining the international articles show that sociopolitical and cultural differences are the main causes of such variations. Finally, our findings shows that a global professional code of ethics is conceivable and can be produced and accepted with minimal conscientious efforts.

关键词： Ethics Societies Engineering profession Australia Europe Organizations

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Visibly accurate model-based binary image compression scheme

Visibly accurate model-based binary image compression scheme

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2011 2nd IEEE International Conference on Signal and image processing Applications, ICSIPA 2011

作者： Alzahir, Saif Image Processing Graphics and Multimedia Lab Computer Science Department UNBC Prince George BC V2N 4Z9 Canada

ISBN: (纸本)9781457702419

In this paper we propose a model-based binary image compression scheme. In this scheme, we merge one-dimensional (1-D) blocks of black pixels of the input binary image with those in consecutive rows into larger blocks using mathematical models that preserve the quality of the image. This process reduces the number of vertices when the image is segmented into rectangles for compression. The top-left and the bottom-right vertices of each generated rectangle are then identified and the coordinates of which are efficiently encoded. The model for merging the blocks was obtained through extracting the data values involving the blocks of various widths and the subjective tolerance of an average viewer. The data values are then plotted on a Cartesian plane and approximated with linear, logarithmic, and polynomial functions. Simulation results show that the images after merging using the proposed model have less number of rectangles without any obvious image distortion and have higher compression ratio those rectangular partitioning methods in the literature. © 2011 IEEE.

关键词： Merging

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A new method in highway route design：joining circular arcs by a single C-Bezier curve with shape paramete

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第4期10卷

作者： Hua-hui CAI Guo-jin WANG Institute of Computer Graphics and Image Processing State Key Lab of CAD & CG Zhejiang University

We constructed a single C-B zier curve with a shape parameter for G2 joining two circular arcs. It was shown that an S-shaped transition curve, which is able to manage a broader scope about two circle radii than the B zier curves, has no curvature extrema, while a C-shaped transition curve has a single curvature extremum. Regarding the two kinds of curves, specific algo- rithms were presented in detail, strict mathematical proofs were given, and the effectiveness of the method was shown by examples. This method has the following three advantages: (1) the pattern is unified; (2) the parameter able to adjust the shape of the tran- sition curve is available; (3) the transition curve is only a single segment, and the algorithm can be formulated as a low order equation to be solved for its positive root. These advantages make the method simple and easy to implement.

关键词： Transition curve Shape parameter C-Bezier curve Monotone curvature

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A new rectangular partitioning based lossless binary image compression scheme

A new rectangular partitioning based lossless binary image c...

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Canadian Conference on Electrical and Computer Engineering 2005

作者： Zahir, Saif Naqvi, Mehmood Image Processing Graphics and Multimedia Lab. Department of Computer Science UNBC Prince George BC V2N 4Z9 Canada

In this paper, we propose a lossless binary image compression scheme that can achieve high compression ratio via partitioning the black regions (one's) of the input image into rectangles. After partitioning, the top-left and the bottom-right vertices of each rectangle are identified and the coordinates of which are efficiently coded. Three different routines are used in this research. The proposed scheme is targeting images, which contain graphs and tables with solid gridlines in the background on the one hand. While on the other hand it is suitable for text images of languages where many characters have dots "nuqta" on them such as Urdu, Persian, and Arabic with big fonts. The proposed scheme has outperformed CCITT run length coding, modified READ, and REC significantly. Also it is faster and simpler to implement than the method reported in reference [6]. © 2005 IEEE.

关键词： image compression

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Architectural style classification of building facade windows

Architectural style classification of building facade window...

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7th International Symposium on Visual Computing, ISVC 2011

作者： Shalunts, Gayane Haxhimusa, Yll Sablatnig, Robert Institute of Computer Aided Automation Computer Vision Lab. Vienna University of Technology Austria Institute of Computer Graphics and Algorithms Pattern Recongition and Image Processing Lab. Vienna University of Technology Austria

Building facade classification by architectural styles allows categorization of large databases of building images into semantic categories belonging to certain historic periods, regions and cultural influences. image databases sorted by architectural styles permit effective and fast image search for the purposes of content-based image retrieval, 3D reconstruction, 3D city-modeling, virtual tourism and indexing of cultural heritage buildings. Building facade classification is viewed as a task of classifying separate architectural structural elements, like windows, domes, towers, columns, etc, as every architectural style applies certain rules and characteristic forms for the design and construction of the structural parts mentioned. In the context of building facade architectural style classification the current paper objective is to classify the architectural style of facade windows. Typical windows belonging to Romanesque, Gothic and Renaissance/Baroque European main architectural periods are classified. The approach is based on clustering and learning of local features, applying intelligence that architects use to classify windows of the mentioned architectural styles in the training stage. © 2011 Springer-Verlag.

关键词： Semantics

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Classification of gothic and baroque architectural elements

Classification of gothic and baroque architectural elements

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2012 19th International Conference on Systems, Signals and image processing, IWSSIP 2012

作者： Shalunts, Gayane Haxhimusa, Yll Sablatnig, Robert Institute of Computer Aided Automation Computer Vision Lab. Vienna University of Technology Austria Institute of Computer Graphics and Algorithms Pattern Recognition and Image Processing Lab. Vienna University of Technology Austria

ISBN: (纸本)9783200023284

Architectural elements are the components and details of buildings. Their unique set, combination, design, construction technique form the architectural style of buildings. Building facade classification by architectural styles is viewed as a task of classifying separate architectural structural elements. In the scope of building facade architectural style classification the current paper targets the problem of classification of Gothic and Baroque architectural elements called tracery, pediment and balustrade. Since certain gradient directions dominate on the shape of each architectural element, discrimination between dominating gradients means classification of architectural elements and thus architectural styles. We use local features to describe gradient directions. Our approach is based on clustering and learning of local features and yields a high classification rate. © 2012 Institute of Telecommunica.

关键词： Classification (of information)

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A fast lossless compression algorithm for Arabic textual images

A fast lossless compression algorithm for Arabic textual ima...

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2011 2nd IEEE International Conference on Signal and image processing Applications, ICSIPA 2011

作者： Alzahir, Saif Graphics Image Processing and Multimedia Lab Computer Science University of Northern British Columbia Prince George BC V2N 4Z9 Canada

ISBN: (纸本)9781457702419

In recent years, an unparalleled volume of textual information was transported over the Internet via email, chatting, blogging, twittering, digital libraries, and information retrieval systems. As the volume of text data has exceeded 40% of the total volume of traffic on the Internet, compressing textual data becomes imperative. Many algorithms were introduced and employed for this purpose including Huffman encoding, arithmetic encoding, the Ziv-Lempel family, Dynamic Markov Compression, and Burrow-Wheeler Transform. In this paper, a novel algorithm for compressing textual images is presented. The algorithm comprises of two parts: (i) a fixed-to-variable codebook;and (ii) row and column reduction coding scheme, RCRC. Simulation results on a large number of Arabic textual images show that this algorithm has a compression ratio of approximately 87%, which exceeds published results including those of JBIG2. © 2011 IEEE.

关键词： Signal encoding

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