publications: - title: "Robust Fusion of Irregularly Sampled Data Using Adaptive Normalized Convolution" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Lucas J. van Vliet" link: "http://homepage.tudelft.nl/e3q6n/" - name: "Klamer Schutte" link: "https://researchr.org/alias/klamer-schutte" year: "2006" doi: "http://www.hindawi.com/journals/asp/2006/083268.abs.html" abstract: "We present a novel algorithm for image fusion from irregularly sampled data. The method is based on the framework of normalized convolution (NC), in which the local signal is approximated through a projection onto a subspace. The use of polynomial basis functions in this paper makes NC equivalent to a local Taylor series expansion. Unlike the traditional framework, however, the window function of adaptive NC is adapted to local linear structures. This leads to more samples of the same modality being gathered for the analysis, which in turn improves signal-to-noise ratio and reduces diffusion across discontinuities. A robust signal certainty is also adapted to the sample intensities to minimize the influence of outliers. Excellent fusion capability of adaptive NC is demonstrated through an application of super-resolution image reconstruction." links: doi: "http://www.hindawi.com/journals/asp/2006/083268.abs.html" "url": "http://www.hindawi.com/journals/asp/2006/083268.abs.html" tags: - "rule-based" - "application framework" - "analysis" - "data-flow" - "data-flow analysis" researchr: "https://researchr.org/publication/10.1155-ASP-2006-83268" cites: 0 citedby: 0 journal: "EURASIP Journal on Applied Signal Processing" volume: "2006" number: "83268" kind: "article" key: "10.1155-ASP-2006-83268" - title: "Paper Fingerprinting Using alpha-Masked Image Matching" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Stuart W. Perry" link: "https://researchr.org/alias/stuart-w.-perry" - name: "Peter A. Fletcher" link: "https://researchr.org/alias/peter-a.-fletcher" year: "2009" month: "December" doi: "http://doi.ieeecomputersociety.org/10.1109/DICTA.2009.82" abstract: "In this paper, we examine the problem of authenticating paper media using the unique fiber structure of each piece of paper (the so-called \"paper fingerprint\"). In particular, we look at methods to authenticate paper media when text has been printed over the authentication zone. We show how alpha-masked correlation [Fitch05] can be applied to this problem and develop a modification to alpha-masked correlation that is more closely matched to the requirements of this problem and produces an improvement in performance. We also investigate two methods of pixel inpainting to remove printed text or marks from the authentication zone and allow ordinary correlation to be performed. We show that these methods can perform as well as alpha-masked correlation. Finally two methods of improving the robustness to forgery are investigated." links: doi: "http://doi.ieeecomputersociety.org/10.1109/DICTA.2009.82" tags: - "paper fingerprint" - "document authentication" researchr: "https://researchr.org/publication/10.1109-DICTA.2009.82" cites: 0 citedby: 0 journal: "Digital Image Computing: Techniques and Applications" volume: "0" kind: "article" key: "10.1109-DICTA.2009.82" - title: "Non-maximum Suppression Using Fewer than Two Comparisons per Pixel" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" year: "2010" doi: "http://dx.doi.org/10.1007/978-3-642-17688-3_41" links: doi: "http://dx.doi.org/10.1007/978-3-642-17688-3_41" dblp: "http://dblp.uni-trier.de/rec/bibtex/conf/acivs/Pham10" researchr: "https://researchr.org/publication/Pham10-1" cites: 0 citedby: 0 pages: "438-451" booktitle: "Advanced Concepts for Intelligent Vision Systems - 12th International Conference, ACIVS 2010, Sydney, Australia, December 13-16, 2010, Proceedings, Part I" editor: - name: "Jacques Blanc-Talon" link: "https://researchr.org/alias/jacques-blanc-talon" - name: "Don Bone" link: "https://researchr.org/alias/don-bone" - name: "Wilfried Philips" link: "https://researchr.org/alias/wilfried-philips" - name: "Dan C. Popescu" link: "https://researchr.org/alias/dan-c.-popescu" - name: "Paul Scheunders" link: "https://researchr.org/alias/paul-scheunders" volume: "6474" series: "Lecture Notes in Computer Science" publisher: "Springer" isbn: "978-3-642-17687-6" kind: "inproceedings" key: "Pham10-1" - title: "Normalized Averaging Using Adaptive Applicability Functions with Applications in Image Reconstruction from Sparsely and Randomly Sampled Data" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Lucas J. van Vliet" link: "http://homepage.tudelft.nl/e3q6n/" year: "2003" doi: "http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2749&spage=485" abstract: "In this paper we describe a new strategy for using local structure adaptive filtering in normalized convolution. The shape of the filter, used as the applicability function in the context of normalized convolution, adapts to the local image structure and avoids filtering across borders. The size of the filter is also adaptable to the local sample density to avoid unnecessary smoothing over high certainty regions. We compared our adaptive interpolation technique with conventional normalized averaging methods. We found that our strategy yields a result that is much closer to the original signal both visually and in terms of MSE, meanwhile retaining sharpness and improving the SNR." links: doi: "http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2749&spage=485" tags: - "context-aware" researchr: "https://researchr.org/publication/PhamV03" cites: 0 citedby: 0 pages: "485-492" booktitle: "Image Analysis, 13th Scandinavian Conference, SCIA 2003, Halmstad, Sweden, June 29 - July 2, 2003, Proceedings" editor: - name: "Josef Bigün" link: "https://researchr.org/alias/josef-big%C3%BCn" - name: "Tomas Gustavsson" link: "https://researchr.org/alias/tomas-gustavsson" volume: "2749" series: "Lecture Notes in Computer Science" publisher: "Springer" isbn: "3-540-40601-8" kind: "inproceedings" key: "PhamV03" - title: "Performance of optimal registration estimators" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Marijn Bezuijen" link: "https://researchr.org/alias/marijn-bezuijen" - name: "Lucas J. van Vliet" link: "http://homepage.tudelft.nl/e3q6n/" - name: "Klamer Schutte" link: "https://researchr.org/alias/klamer-schutte" - name: "Cris L. Luengo" link: "www.cb.uu.se/~cris/" year: "2005" doi: "http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.78.9723" abstract: "This paper derives a theoretical limit for image registration and presents an iterative estimator that achieves the limit. The variance of any parametric registration is bounded by the Cramer-Rao bound (CRB). This bound is signal-dependent and is proportional to the variance of input noise. Since most available registration techniques are biased, they are not optimal. The bias, however, can be reduced to practically zero by an iterative gradientbased estimator. In the proximity of a solution, this estimator converges to the CRB with a quadratic rate. Images can be brought close to each other, thus speedup the registration process, by a coarse-to-fine multi-scale registration. The performance of iterative registration is finally shown to significantly increase image resolution from multiple low resolution images under translational motions." links: doi: "http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.78.9723" researchr: "https://researchr.org/publication/Pham05performanceof" cites: 0 citedby: 0 booktitle: "Visual Information Processing XIV." number: "5817" series: "SPIE" publisher: "SPIE" kind: "inproceedings" key: "Pham05performanceof" - title: "Non-maximum Suppression Using Fewer than Two Comparisons per Pixel" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" year: "2010" month: "December" doi: "http://www.springerlink.com/content/lv8uj7p139015jj5" abstract: "Non-Maximum Suppression (NMS) is the task of finding all local maxima in an image. This is often solved using gray-scale image dilation, which requires at least 6 comparisons per pixel in 2-D. We present two solutions that use fewer than 2 comparisons per pixel with little memory overhead. The first algorithm locates 1-D peaks along the image's scan-line and compares each of these peaks against its 2-D neighborhood in a spiral scan order. The second algorithm selects local maximum candidates from the maxima of non-overlapping blocks of one-fourth the neighborhood size. Both algorithms run considerably faster than current best methods in the literature when applied to feature point detection. Matlab code of the proposed algorithms is provided for evaluation purposes." links: doi: "http://www.springerlink.com/content/lv8uj7p139015jj5" tags: - "Spiral" researchr: "https://researchr.org/publication/10.1007-978-3-642-17688-3" cites: 0 citedby: 0 volume: "6474" pages: "438-451" kind: "article" key: "10.1007-978-3-642-17688-3" - title: "Paper Fingerprinting Using alpha-Masked Image Matching" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Stuart W. Perry" link: "http://www.cisra.com.au/" - name: "Peter A. Fletcher" link: "http://www.cisra.com.au/" year: "2009" doi: "http://doi.ieeecomputersociety.org/10.1109/DICTA.2009.82" abstract: "In this paper, we examine the problem of authenticating paper media using the unique fibre structure of each piece of paper (the so-called ”paper fingerprint”). In particular, we look at methods to authenticate paper media when text has been printed over the authentication zone. We show how alpha-masked correlation [Fitch2005] can be applied to this problem and develop a modification to alpha-masked correlation that is more closely matched to the requirements of this problem and produces an improvement in performance. We also investigate two methods of pixel inpainting to remove printed text or marks from the authentication zone and allow ordinary correlation to be performed. We show that these methods can perform as well as alpha-masked correlation. Finally two methods of improving the robustness to forgery are investigated." links: doi: "http://doi.ieeecomputersociety.org/10.1109/DICTA.2009.82" researchr: "https://researchr.org/publication/PhamPF09" cites: 0 citedby: 0 pages: "439-446" booktitle: "DICTA 2009, Digital Image Computing: Techniques and Applications, 1-3 December 2009, Melbourne, Australia" publisher: "IEEE Computer Society" isbn: "978-0-7695-3866-2" kind: "inproceedings" key: "PhamPF09" - title: "Bidirectional bias correction for Gradient-Based Shift Estimation" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Matthew Duggan" link: "https://researchr.org/alias/matthew-duggan" year: "2008" doi: "http://dx.doi.org/10.1109/ICIP.2008.4711883" abstract: "This paper characterizes the bias of a Gradient-Based Shift Estimator (GBSE) and proposes a novel scheme to correct for the bias. The bias of GBSE comes from an inaccurate estimate of the image gradient energy, which is due to noise, aliasing and built-in low-pass filtering. For subpixel shift, the bias is linearly proportional to the true shift. The linear bias factor can be blindly estimated using two or more subpixel shift estimates of the same image pair, each estimate is performed on a slightly shifted version of the second image. Compared to the original GBSE, the new method reduces the bias by half at the same time improving the precision." links: doi: "http://dx.doi.org/10.1109/ICIP.2008.4711883" tags: - "rule-based" - "shift estimation bias" researchr: "https://researchr.org/publication/PhamD08" cites: 0 citedby: 0 pages: "829-832" booktitle: "Proceedings of the International Conference on Image Processing, ICIP 2008, October 12-15, 2008, San Diego, California, USA" publisher: "IEEE" kind: "inproceedings" key: "PhamD08" - title: "Spatiotonal adaptivity in Super-resolution from undersampled image sequences" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" year: "2006" month: "October" abstract: "This thesis concerns the use of spatial and tonal adaptivity in improving the resolution of aliased image sequences under scene or camera motion. Each of the five content chapters focuses on a different subtopic of super-resolution: image registration (chapter 2), image fusion (chapter 3 and 4), super-resolution restoration (chapter 5), and super-resolution synthesis (chapter 6). Chapter 2 derives the Cramer-Rao lower bound of image registration and shows that iterative gradient-based estimators achieve this performance limit. Chapter 3 presents an algorithm for image fusion of irregularly sampled and uncertain data using robust normalized convolution. The size and shape of the fusion kernel is adapted to local curvilinear structures in the image. Each data sample is assigned an intensity-related certainty value to limit the influence of outliers. Chapter 4 presents two fast implementations of the signal-adaptive bilateral filter. The xy-separable implementation filters the image along sampling axes, while the uv-separable implementation filters the image along gauge coordinates. Chapter 5 presents a robust image restoration method using Gaussian error norm rather than quadratic error norm. The robust solution resembles the maximum-likelihood solution under Gaussian noise, and it is not susceptible to outliers. A series of objective quality measures confirms the superiority of this solution to current super-resolution algorithms in the literature. Chapter 6 proposes a super-resolution synthesis algorithm in the DCT domain. The algorithm requires a high-resolution image of similar content to be used as texture source for the low-resolution input image." note: "ISBN 9075691149" tags: - "rule-based" - "data-flow" - "source-to-source" - "peer-to-peer" - "open-source" researchr: "https://researchr.org/publication/Pham-2006-PhdThesis" cites: 0 citedby: 0 school: "Quantitative Imaging Group, Delft University of Technology" type: "PhD in Image analysis" address: "Quantitative Imaging Group, Lorentzweg 1, 2628 CJ Delft, The Netherlands" advisor: - name: "Lucas J. van Vliet" link: "https://researchr.org/alias/lucas-j.-van-vliet" kind: "phdthesis" key: "Pham-2006-PhdThesis" - title: "Resolution enhancement of low-quality videos using a high-resolution frame" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Lucas J. van Vliet" link: "http://homepage.tudelft.nl/e3q6n/" - name: "Klamer Schutte" link: "https://researchr.org/alias/klamer-schutte" year: "2006" doi: "http://dx.doi.org/10.1117/12.643489" abstract: "This paper proposes an example-based Super-Resolution (SR) algorithm of compressed videos in the Discrete Cosine Transform (DCT) domain. Input to the system is a Low-Resolution (LR) compressed video togetherwith a High-Resolution (HR) still image of similar content. Using a training set of corresponding LR-HR pairs of image patches from the HR still image, high-frequency details are transferred from the HR source to the LR video. The DCT-domain algorithm is much faster than example-based SR in spatial domain6 because of a reduction in search dimensionality, which is a direct result of the compact and uncorrelated DCT representation. Fast searching techniques like tree-structure vector quantization16 and coherence search1 are also key to the improved efficiency. Preliminary results on MJPEG sequence show promising result of the DCT-domain SR synthesis approach. " links: doi: "http://dx.doi.org/10.1117/12.643489" "url": "http://link.aip.org/link/?PSI/6077/607708/1" tags: - "rule-based" - "source-to-source" - "search" - "systematic-approach" - "open-source" researchr: "https://researchr.org/publication/pham%3A607708" cites: 0 citedby: 0 booktitle: "Visual Communications and Image Processing SPIE 6077" volume: "6077" number: "1" publisher: "SPIE" kind: "inproceedings" key: "pham:607708" - title: "Separable bilateral filtering for fast video preprocessing" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Lucas J. van Vliet" link: "http://homepage.tudelft.nl/e3q6n/" year: "2005" doi: "http://doi.ieeecomputersociety.org/10.1109/ICME.2005.1521458" abstract: "Bilateral filtering is an edge-preserving filtering technique that employs both geometric closeness and photometric similarity of neighboring pixels to construct its filter kernel. Multi-dimensional bilateral filtering is computationally expensive because the adaptive kernel has to be recomputed at every pixel. In this paper, we present a separable implementation of the bilateral filter. The separable implementation offers equivalent adaptive filtering capability at a fraction of execution time compared to the traditional filter. Because of this efficiency, the separable bilateral filter can be used for fast preprocessing of images and videos. Experiments show that better image quality and higher compression efficiency is achievable if the original video is preprocessed with the separable bilateral filter." links: doi: "http://doi.ieeecomputersociety.org/10.1109/ICME.2005.1521458" researchr: "https://researchr.org/publication/PhamV05" cites: 0 citedby: 0 pages: "454-457" booktitle: "Proceedings of the 2005 IEEE International Conference on Multimedia and Expo, ICME 2005, July 6-9, 2005, Amsterdam, The Netherlands" publisher: "IEEE" kind: "inproceedings" key: "PhamV05" - title: "Influence of signal-to-noise ratio and point spread function on limits of superresolution" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Lucas J. van Vliet" link: "https://researchr.org/alias/lucas-j.-van-vliet" - name: "Klamer Schutte" link: "https://researchr.org/alias/klamer-schutte" year: "2006" doi: "http://dx.doi.org/10.1117/12.586574" abstract: "This paper presents a method to predict the limit of possible resolution enhancement given a sequence of lowresolution images. Three important parameters influence the outcome of this limit: the total Point Spread Function (PSF), the Signal-to-Noise Ratio (SNR) and the number of input images. Although a large number of input images captured by a system with a narrow PSF and a high SNR are desirable, these conditions are often not achievable simultaneously. To improve the SNR, cameras are designed with near optimal quantum efficiency and maximum fill-factor. However, the latter widens the system PSF, which puts more weight on the deblurring part of a super-resolution (SR) reconstruction algorithm. This paper analyzes the contribution of each input parameters to the SR reconstruction and predicts the best attainable SR factor for given a camera setting. The predicted SR factor agrees well with an edge sharpness measure computed from the reconstructed SR images. A sufficient number of randomly positioned input images to achieve this limit for a given scene can also be derived assuming Gaussian noise and registration errors." links: doi: "http://dx.doi.org/10.1117/12.586574" dblp: "http://dblp.uni-trier.de/rec/bibtex/conf/ipas/PhamVS06" researchr: "https://researchr.org/publication/PhamVS06" cites: 0 citedby: 0 pages: "169-180" booktitle: "Image Processing: Algorithms and Systems IV, 17 January 2006, San Jose, California, USA" editor: - name: "Edward R. Dougherty" link: "https://researchr.org/alias/edward-r.-dougherty" - name: "Jaakko Astola" link: "https://researchr.org/alias/jaakko-astola" - name: "Karen O. Egiazarian" link: "https://researchr.org/alias/karen-o.-egiazarian" volume: "5672" series: "SPIE Proceedings" publisher: "SPIE" kind: "inproceedings" key: "PhamVS06" - title: "Robust Fusion of Irregularly Sampled Data Using Adaptive Normalized Convolution" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Lucas J. van Vliet" link: "https://researchr.org/alias/lucas-j.-van-vliet" - name: "Klamer Schutte" link: "https://researchr.org/alias/klamer-schutte" year: "2006" doi: "http://dx.doi.org/10.1155/ASP/2006/83268" links: doi: "http://dx.doi.org/10.1155/ASP/2006/83268" dblp: "http://dblp.uni-trier.de/rec/bibtex/journals/ejasp/PhamVS06" tags: - "data-flow" researchr: "https://researchr.org/publication/PhamVS06-0" cites: 0 citedby: 0 journal: "EURASIP J. Adv. Sig. Proc." volume: "2006" kind: "article" key: "PhamVS06-0" - title: "Robust super-resolution by minimizing a Gaussian-weighted L2 error norm" author: - name: "Tuan Q. Pham" link: "http://www.cisra.com.au" - name: "Lucas J. van Vliet" link: "http://homepage.tudelft.nl/e3q6n/" - name: "Klamer Schutte" link: "https://researchr.org/alias/klamer-schutte" year: "2008" doi: "http://dx.doi.org/10.1088/1742-6596/124/1/012037" abstract: "Super-resolution restoration is the problem of restoring a high-resolution scene from multiple degraded low-resolution images under motion. Due to imaging blur and noise, this problem is ill-posed. Additional constraints such as smoothness of the solution via regularization is often required to obtain a stable solution. While adding a regularization term to the cost function is a standard practice in image restoration, we propose a restoration algorithm that does not require this extra regularization term. The robustness of the algorithm is achieved by a Gaussian-weighted L2 -norm in the data misfit term that does not response to intensity outliers. With the outliers suppressed, our solution behaves similarly to a maximum-likelihood solution in the presence of Gaussian noise. The effectiveness of our algorithm is demonstrated with super-resolution restoration of real infrared image sequences under severe aliasing and intensity outliers." links: doi: "http://dx.doi.org/10.1088/1742-6596/124/1/012037" "url": "http://stacks.iop.org/1742-6596/124/i=1/a=012037" tags: - "robust maximum likelihood" - "constraints" - "data-flow" researchr: "https://researchr.org/publication/1742-6596-124-1-012037" cites: 0 citedby: 0 journal: "Journal of Physics: Conference Series" volume: "124" number: "1" kind: "article" key: "1742-6596-124-1-012037"