Chotikakamthorn, Nopporn

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Chotikakamthorn, Nopporn
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Chotikakamthorn, N.
Chotikakamthornb, Nopporn
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nopporn.ch@kmitl.ac.th

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    Performance of Bayesian-based digital matting techniques
    (2007-12-01)
    Cumpim, Chaipichit
    ;
    Chotikakamthorn, Nopporn
    Statistical-based digital matting of natural background is considered in this paper. Performance of the original Bayesian-based matting method has been studied. It is shown that the performance depends on the algorithm initial condition as well as a noise variance parameter. Two initialization methods have been considered. The first one obtains initial value from Ruzon's maximum likelihood method, while the second one employs the centers of foreground and background color clusters as the initial value. Both methods were found to offer improved performance. In addition, optimum choice of the noise variance was found to vary from one image to another. An alternative formulation of a Bayesian-based digital matting technique which does not contain the noise variance parameter is described. It was found to yield results comparable to the original method for most of the test cases. ©2007 IEEE.
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    Fast haptic simulation of brittle object using bounded force propagation model
    (2008-12-01)
    Somrang, Nontapol
    ;
    Chotikakamthorn, Nopporn
    ;
    Jirapatehandej, Siraset
    In this paper, a method for real-time simulation of brittle object with haptic force feedback is described. Based on the rigid-constraint model, originally developed for visual-only image synthesis, a virtual object is represented as a set of point- masses connected by distance-preserving linear constraints. The drawback of the original method is that it is time consuming and not suitable for real-time haptic simulation. In this paper, a bounded force propagation model is developed to reduce calculation time as required by the original method. In addition, a haptic-endpoint position prediction method is applied to prepare the simulation system for the calculation required by the method. These refinements allow the brittle object simulation method to be applicable to real-time interactive applications with haptic force feedback. © 2008 IEEE.
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    Evaluation the efficacy of Computer - Based training using tangible user interface for Low-Function children with autism
    (2008-12-01)
    Sitdhisanguan, Karanya
    ;
    Chotikakamthorn, Nopporn
    ;
    Dechaboon, Ajchara
    ;
    Out, Patcharaporn
    Recently, the number of children having autism disorder increases rapidly all over the world. Computerbased training (CBT) has been applied to autism spectrum disorder treatment. Most CBT applications are based on the standard WIMP interface. However, recent study suggests that a Tangible User Interface (TUI) is easier to use for children with autism than the WIMP interface. In this paper, the efficiency of the TUI training system is considered, in comparison with a conventional method of training basic geometric shape classification. A CBT system with TUI was developed using standard computer equipment and a consumer video camera. The experiment was conducted to measure learning efficacy of the new system and the conventional training method. The results show that, under the same time constraint, children with autism who practiced with the new system were able to learn more shapes than those participating in the conventional method. © 2008 IEEE.
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    Comparative study of two projective-invariant digital watermarking methods using cross-ratios and line intersections
    (2005-12-01)
    Pantuwong, Natapon
    ;
    Chotikakamthorn, Nopporn
    Recently, based on a set of four coplanar points, a projective-invariant digital watermarking has been developed. A combination of line intersection and the cross-ratio relationship of collinear points is used to calculate watermarking embedding locations. The four coplanar points used to derive embedding locations can be obtained from either the image corners or the feature points extracted from the image content. It is shown in this paper that based on the same principle, an alternative algorithm for calculating the watermark embedding locations improves computational efficiency. The proposed method heavily uses the cross-ratio relationship of collinear points, while minimizing the use of line intersection in obtaining embedding locations. This is in contrast with the original method, where embedding locations are mainly obtained from intersections of line pairs. Both analytical and experimental results are provided to demonstrate the improvement. © 2005 IEEE.
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    A light-pointing method for virtual object selection and manipulation in a monoscopic viewing system
    (2005-12-01)
    Kanjanasupark, Pornchai
    ;
    Chotikakamthorn, Nopporn
    Virtual object selection and re-location are two basic object manipulations that can be found in most VR/VE applications. Many interaction metaphors have been developed for object manipulation in VR/VE environments. Of particular interest is the ray-casting method. The method applies a light ray metaphor in selecting and moving a virtual object. However, the method implicitly requires a stereoscopic viewing system to be efficiently use. With a monoscopic viewing system, inefficiency of the method in terms of task completion time is demonstrated in this paper. For a system using a monoscopic viewing device, a light-pointing method based on a laser-pointer metaphor is proposed to alleviate the shortcoming of the original ray-casting method. Compared with the ray-casting method, it was found from the experiment that the proposed method is noticeably more efficient in terms of task completion time. © 2005 IEEE.
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    An interatvie stereoscopic viewing system using fast vision-based leg end-point position estimation
    (2005-12-01)
    Phutphuek, Narongsak
    ;
    Chotikakamthorn, Nopporn
    In this paper, a problem of interactive stereoscopic display is considered. To provide a stereo image pair with correct viewing angle, a stereoscopic system must be able to identify a viewer spatial location. A fast and low-cost viewer location estimation method using a single video camera is described in this paper. The method tracks a viewer's standing position by estimating his/her leg end-point on the floor. The so-obtained position is then transformed to a 3D coordinate by using a planar homographic projection. Because the estimated viewer position is noisy, a smoothing and semi-interactive updating algorithm is developed to reduce a flicker caused by the imprecise estimate. © 2005 IEEE.
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    A joint controller-simulator programming by demonstration method for PLC devices
    (2006-12-01)
    Changsakol, Phissanu
    ;
    Chotikakamthorn, Nopporn
    ;
    Wongwirat, Olarn
    In this paper, a problem of visual programming of PLC (programmable logic controller) devices is described. A programming by demonstration method is developed so that a problem-domain expert can program such devices without computer programming skill. The method is novel in the sense that, unlike other programming-by-demonstration methods, it requires little a priori knowledge of the controlled system model, nor it needs to interact with a real system. A simulation model, which captures the laws of nature governing the system behavior, is jointly programmed with a control device (PLC). A PLC programming tool, developed based on the proposed joint controller-simulator programming by demonstration paradigm, can generate a high-level structure text program code, from the demonstrated actions as performed by a user. © 2006 IEEE.
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    Seeing by drawing: Use of a force-feedback device for conveying basic geometric visual information
    (2000-12-01)
    Chotikakamthorn, Nopporn
    ;
    Hongboonme, Nattavadee
    In this paper, the problem of using a force-feedback device to display basic geometric information is considered. Two visual-haptic transformation methods are applied to display geometric-shape properties by a point-contact force-reflective device. With the first method, movement of a user's finger tip, attached to a force-feedback device's thimble, is limited to points on a contour representing an outline of the (1-D or 2-D) geometric shape under display. In the second method, a drawing force is applied to a thimble, to move a user's finger along the contour corresponding to the displayed shape. Drawing speed is adjusted to reflect some properties of the displayed data curve, such as evolution of its first or second derivatives over time or spatial reference axis. Implementation aspects of the two methods are discussed. Efficiency of the described haptic display methods has been investigated through experiments with basic geometric outline shapes and scientific data.
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    Attacks on feature-based affine-invariant watermarking methods
    (2005-12-01)
    Chotikakamthorn, Nopporn
    ;
    Pantuwong, Natapon
    A class of attacks targeting at a feature-based affine-invariant digital watermarking technique is addressed in this paper. First, it is pointed out that the use of feature points to revert an affine transform operation is equivalent to the use of a known image size or boundary for image normalization. Therefore, any method based on feature points suffers from point shifting in much the same manner as how the image normalization scheme suffers from cropping or reframing. Some simple methods to perform a (feature) point shifting attack are next described. Although use of a sufficient large number of candidate feature points can solve the problem, the paper further points out that this solution, like any secure template-based watermarking method, results in high detection complexity. A two-stage search scheme is proposed to avoid the attack, while retaining the overall detection complexity to a reasonable level. © 2005 IEEE.
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    Improved dynamic gesture segmentation for Thai sign language translation
    (2004-12-27)
    Werapan, Worawit
    ;
    Chotikakamthorn, Nopporn
    Sign languages normally make use of both static and dynamic gestures to achieve communication goal. In automated continuous gesture recognition, one of the problems found is how to separate a transitional gesture from a meaningful dynamic gesture. In addition, a variation in speed, absolute position and orientation of a dynamic gesture makes an automatic recognition task nontrivial. This paper proposes a segmentation method that alleviates these problems. The method is based on the fact that many (meaningful) dynamic gestures as appeared in Thai and other sign languages, are performed in an approximately (quasi) periodic manner. Therefore, such dynamic gestures can be distinguished from a transitional gesture by means of Fourier analysis, performed on samples (discrete signal) of hand shapes, positions, and orientation. The analysis, however, requires a good choice of data sample windowing. This paper describes a pre-processing method for estimation of the dynamic gesture data windowing period. The proposed method helps improving the accuracy of segmenting hand shape and location data samples into static, periodic, and non-periodic gestures. In addition, accuracy of the feature extracted from the Fourier analysis of a dynamic gesture signal is improved, thus increasing the recognition rate. Experimental results performed on a real data are included.