Changsoo Je

PolyDepth: Real-time penetration depth computation using iterative contact-space projection

We present a real-time algorithm that finds the Penetration Depth (PD) between general polygonal models based on iterative and local optimization techniques. Given an in-collision configuration of an object in configuration space, we find an initial collision-free configuration using several methods such as centroid difference, maximally clear configuration, motion coherence, random configuration, and sampling-based search. We project this configuration on to a local contact space using a variant of continuous collision detection algorithm and construct a linear convex cone around the projected configuration. We then formulate a new projection of the in-collision configuration onto the convex cone as a Linear Complementarity Problem (LCP), which we solve using a type of Gauss-Seidel iterative algorithm. We repeat this procedure until a locally optimal PD is obtained. Our algorithm can process complicated models consisting of tens of thousands triangles at interactive rates.

Optimized hierarchical block matching for fast and accurate image registration

Recently the camera resolution has been highly increased, and the registration between high-resolution images is computationally expensive even by using hierarchical block matching. This paper presents a novel optimized hierarchical block matching algorithm in which the computational cost is minimized for the scale factor and the number of levels in the hierarchy. The algorithm is based on a generalized version of the Gaussian pyramid and its inter-layer transformation of coordinates. The search window size is properly determined to resolve possible error propagation in hierarchical block matching. In addition, we also propose a simple but effective method for aligning colors between two images based on color distribution adjustment as a preprocessing. Simplifying a general color imaging model, we show much of the color inconsistency can be compensated by our color alignment method. The experimental results show that the optimized hierarchical block matching and color alignment methods increase the block matching speed and accuracy, and thus improve image registration. Using our algorithm, it takes about 1.28s for overall registration process with a pair of images in 5 mega-pixel resolution.

Multi-projector color structured-light vision

Research interest in rapid structured-light imaging has grown increasingly for the modeling of moving objects, and a number of methods have been suggested for the range capture in a single video frame. The imaging area of a 3D object using a single projector is restricted since the structured light is projected only onto a limited area of the object surface. Employing additional projectors to broaden the imaging area is a challenging problem since simultaneous projection of multiple patterns results in their superposition in the light-intersected areas and the recognition of original patterns is by no means trivial. This paper presents a novel method of multi-projector color structured-light vision based on projector-camera triangulation. By analyzing the behavior of superposed-light colors in a chromaticity domain, we show that the original light colors cannot be properly extracted by the conventional direct estimation. We disambiguate multiple projectors by multiplexing the orientations of projector patterns so that the superposed patterns can be separated by explicit derivative computations. Experimental studies are carried out to demonstrate the validity of the presented method. The proposed method increases the efficiency of range acquisition compared to conventional active stereo using multiple projectors.

Disparity-based space-variant image deblurring

Obtaining a good-quality image requires exposure to light for an appropriate amount of time. If there is camera or object motion during the exposure time, the image is blurred. To remove the blur, some recent image deblurring methods effectively estimate a point spread function (PSF) by acquiring a noisy image additionally, and restore a clear latent image with the PSF. Since the groundtruth PSF varies with the location, a blockwise approach for PSF estimation has been proposed. However, the block to estimate a PSF is a straightly demarcated rectangle which is generally different from the shape of an actual region where the PSF can be properly assumed constant. We utilize the fact that a PSF is substantially related to the local disparity between two views. This paper presents a disparity-based method of space-variant image deblurring which employs disparity information in image segmentation, and estimates a PSF, and restores a latent image for each region. The segmentation method firstly over-segments a blurred image into sufficiently many regions based on color, and then merges adjacent regions with similar disparities. Experimental results show the effectiveness of the proposed method.

BREN: body reflection essence-neuter model for separation of reflection components

We propose a novel reflection color model consisting of body essence and (mixed) neuter, and present an effective method for separating dichromatic reflection components using a single image. Body essence is an entity invariant to interface reflection, and has two degrees of freedom unlike hue and maximum chromaticity. As a result, the proposed method is insensitive to noise and proper for colors around CMY (cyan, magenta, and yellow) as well as RGB (red, green, and blue), contrary to the maximum chromaticity-based methods. Interface reflection is separated by using a Gaussian function, which removes a critical thresholding problem. Furthermore, the method does not require any region segmentation. Experimental results show the efficacy of the proposed model and method.

Homographic p-norms

Images often need to be aligned in a single coordinate system, and homography is one of the most efficient geometric models to align images. This paper presents homographic p-norms, scalar metrics of homographic image transformation, and to the best of our knowledge these are the most rigorous definition of scalar metrics quantifying homographic image transformations. We first define a metric between two homography matrices, and show it satisfies metric properties. Then we propose metrics of a single homography matrix for a general planar region, and ones for a usual rectangle image. For use of the proposed metrics, we provide useful homographic 2-norm expressions derived from the definition of the metrics, and compare the approximation errors of the metrics with respect to the exact metric. As a result, the discrete version of the metric obtained by pixel-wise computation is greatly close to the exact metric. The proposed metrics can be applied to evaluation of transformation magnitude, image closeness estimation, evaluation of camera pose difference, selection of image pair in stereo vision, panoramic image mosaic, and deblurring. Experimental results show the efficacy of the proposed metrics. Graphical abstractDisplay Omitted HighlightsWe propose homographic p-norms, metrics of homographic image transformation.We show that homographic p-norms satisfy metric properties.For use of the metrics, we provide several homographic 2-norm expressions.We compare their approximation errors, and validate the efficacy of the metrics.The metrics can be applied to various image processing and analysis tasks.

Color-stripe structured light robust to surface color and discontinuity

Multiple color stripes have been employed for structured light-based rapid range imaging to increase the number of uniquely identifiable stripes. The use of multiple color stripes poses two problems: (1) object surface color may disturb the stripe color and (2) the number of adjacent stripes required for identifying a stripe may not be maintained near surface discontinuities such as occluding boundaries. In this paper, we present methods to alleviate those problems. Log-gradient filters are employed to reduce the influence of object colors, and color stripes in two and three directions are used to increase the chance of identifying correct stripes near surface discontinuities. Experimental results demonstrate the effectiveness of our methods.

Mouth map-assisted localisation of ASM lip landmarks

The extended active shape models have shown their robustness in facial landmarks fitting. However, we often meet substantial errors of lip landmarks fitting mostly due to teeth boundaries. An attempt to reduce the errors using high-quality mouth maps has been made recently. Since most existing facial datasets cannot produce high-quality mouth maps, use of mouth maps should be careful not to bring even more serious errors from them. Unlike the existing scheme using the mouth map, we use the mouth map not for profile model but only for better initialisation of landmarks right before profile matching. As a result, the proposed method attains higher accuracies compared to the original Stasm 4 and the existing method using the mouth map. Experimental studies validate the effectiveness of the proposed method. Since the proposed method uses the mouth map only for initialisation, it requires neither additional task in training nor high-quality mouth maps.

Homographic p-norms: Metrics of homographic image transformation

T paper introduces the fuzzy PID control method for outer loop voltage of bidirectional DC-DC converter. In recent years, with the rapid development of new energy technology, bidirectional DC-DC converter has been widely used in the new energy vehicles. Bidirectional DC-DC converter is a kind of strongly nonlinear system. How to make the converter system work steadily and fast is a hot research area. A bidirectional DC-DC converter is a strongly nonlinear system. The traditional PID control is known for its simple algorithm and easy design, but the parameters cannot do well in dynamic performance and static performance, which affect the final control effect. Taking the Boost converter as an example, a PI control for the voltage inner loop and a Fuzzy PID control for the voltage outer loop was proposed to improve disadvantages of the traditional PID control. And the Boost simulation experiment was built in Matlab/Simulink. The simulation results show that compared with the traditional PID control, this control method can effectively solve the nonlinear problems of bidirectional DC-DC converter, improve the response of bidirectional DC-DC converter, and reduce the output voltage fluctuation.S and natural scientists have used the complexity paradigm to address issues of the complexity and dynamism of phenomena which hitherto in traditional approaches had been made invisible or had been regarded as aberrant – thereby adding to our explanatory and manipulative power. As Appadurai (1996) calls for a human version of complexity theory in order to further the theory of global cultural interactions, Takahashi (2009) has applied a non-linear, non-reductionist model to human communication, using the ethnographic method, which is a non-linear methodology. Takahashi has provided an integrated framework for the demonstration of three dimensions of complex systems: individuals, social groups and cultures and the paths of dynamic interaction between these in terms of interactivity, self-organisation, adaptivity and the notion of the edge of chaos, thus contributing to the idea of a human version of complexity theory. There are numerous complex systems that exist among the micro and macro levels and each level is not discrete but rather is intraand interconnected and moreover dynamically interacts with the others. In this presentation, we will demonstrate the complex model of communication with some computer images to understand the diversity, dynamism and complexity of human communication in the global digital world.

A Method for Speech Dereverberation Based on an Image Deblurring Algorithm Using the Prior of Speech Magnitude Gradient Distribution in the Time-Frequency Domain

We propose a speech dereverberation method in the time-frequency domain, based on an image deblurring algorithm. A reverberant speech magnitude can be modeled as a convolution of a clean speech with a reverberation filter in time-frequency domain. Then, dereverberation problem can be regarded as that of image deblurring. Therefore, the proposed method estimates the clean speech magnitude in the time-frequency domain by using the fast image deconvolution method with priors on sparsity of the clean speech magnitude gradient and exponentially decaying property of reverberation filters along the time axis. Then, scaling the reverberation speech magnitude by a mask obtained from the estimated clean one performs dereverberation. Experimental results show that the described method can enhance speech.