Wen-Kai Tai

A novel method for detecting lips, eyes and faces in real time

This paper presents a real-time face detection algorithm for locating faces in images and videos. This algorithm finds not only the face regions, but also the precise locations of the facial components such as eyes and lips. The algorithm starts from the extraction of skin pixels based upon rules derived from a simple quadratic polynomial model. Interestingly, with a minor modification, this polynomial model is also applicable to the extraction of lips. The benefits of applying these two similar polynomial models are twofold. First, much computation time are saved. Second, both extraction processes can be performed simultaneously in one scan of the image or video frame. The eye components are then extracted after the extraction of skin pixels and lips. Afterwards, the algorithm removes the falsely extracted components by verifying with rules derived from the spatial and geometrical relationships of facial components. Finally, the precise face regions are determined accordingly. According to the experimental results, the proposed algorithm exhibits satisfactory performance in terms of both accuracy and speed for detecting faces with wide variations in size, scale, orientation, color, and expressions.

New approach for static gesture recognition

Static gestures can convey certain meanings and act as specific transitions in dynamic gestures. Therefore, recognizing static gestures is one of the most important aspects of gesture recognition. In this paper, a new approach is presented for recognizing static gestures based on Zernike moments (ZMs) and pseudo-Zernike moments (PZMs). The binary hand silhouette is first accommodated with a minimum bounding circle (MBC). The binary hand silhouette is then decomposed into the finger part and the palm part by morphological operations according to the radius of the MBC. After that, the ZMs & PZMs of the finger part and the palm part with different importance, respectively, are computed based on the center of the MBC. Finally, 1-nearest neighbor techniques are used to perform feature matching between an input feature vector and stored feature vectors for static gesture identification. Results show that the proposed approach performs better than previous methods based on conventional ZMs & PZMs in recognizing static gestures. The proposed technique could be useful in improving the recognition rate, of static gestures.

Feature alignment approach for hand posture recognition based on curvature scale space

One of the most important aspects of gesture recognition is recognizing hand postures. Much research has been devoted to extracting reliable features for hand posture recognition. In this paper, a new feature alignment approach for hand posture recognition based on curvature scale space (CSS) is presented. The basis point for alignment is based on the two-dimensional distribution of a coordinate-peak set of the CSS image instead of on the coordinate with the maximal peak. A convolution operation is performed with the sequence of a coordinate-peak set and a predefined function. The coordinate with the maximal convolution value is designated as a basis point for aligning the CSS features of the hand posture. Results show that the proposed approach performs well in recognizing hand postures. Furthermore, the proposed approach is more accurate than previous methods based on conventional features.

A simple GPU-based approach for 3D Voronoi diagram construction and visualization

Abstract In this paper we propose a simple GPU-based approach for discrete incremental approximation of 3D Voronoi diagram. By constructing region maps via GPU. Nearest sites, space clustering, and shortest distance query can be quickly answered by looking up the region map. In addition, we propose another representation of the 3D Voronoi diagram for visualization.

A flexible 3D slicer for voxelization using graphics hardware

In this paper we present a simple but general 3D slicer for voxelizing polygonal model. Instead of voxelizing a model by projecting and rasterizing triangles with clipping planes, the distance field is used for more accurate and stable voxelization. Distance transform is used with triangles on voxels of each slice. A voxel is marked with opacity only when the shortest distance between it and triangles is judged as intersection. With advanced programmable graphics hardware assistance, surface and solid voxelization are feasible and more efficient than on a CPU.

Synthesizing transition textures on succession patterns

Synthesizing transition textures on succession patterns for displaying visually acceptable terrain is essential to applications such as computer games. In this paper, we exploited the Game of Life model to simulate successions on terrain to show that a good-looking profile can appear quickly and easily. Based on the proposed modified patch-based sampling texture synthesis approach, the basic types of transition textures on a succession pattern can be well synthesized. This method first generates a well-shaped transition cut along the source texture. Next, the feature maps of the source texture and the target texture are used to determine complementary patches from the target texture that will fit well along the sources transition cut. As the experimental results show, only a few input textures are required by our approach to synthesize plenty of tileable transition textures which are useful for obtaining vivid terrain while consuming only a small amount of texture memory.

An improved data hiding approach for polygon meshes

We present an improved technique for data hiding in polygonal meshes, which is based on the work of Bogomjakov et al. (Comput. Graph. Forum 27(2):637–642, 2008). Like their method, we use an arrangement on primitives relative to a reference ordering to embed a message. But instead of directly interpreting the index of a primitive in the reference ordering as the encoded/decoded bits, our method slightly modifies the mapping so that our modification doubles the chance of encoding an additional bit compared to Bogomjakov et al.’s (Comput. Graph. Forum 27(2):637–642, 2008). We illustrate the inefficiency in the original mapping of Bogomjakov et al. (Comput. Graph. Forum 27(2):637–642, 2008) with an intuitive representation using a binary tree.Although both methods have the same minimal and maximal capacities and are both only one bit per primitive less than optimal, our method improves the average capacity up to 0.63 bits per primitive. Our embedding and extraction algorithms are just as simple to implement and just as efficient, O(n), as those of Bogomjakov et al. (Comput. Graph. Forum 27(2):637–642, 2008).

A Talking Face Driven by Voice using Hidden Markov Model

In this paper, we utilized Hidden Markov Model (HMM) as a mapping mechanism between two different kinds of correlated signals. Specifically, we developed a voice-driven talking head system by exploiting the physical relationships between the shape of the mouth and the sound that is produced. The proposed system can be easily trained and a talking head can be efficiently animated. In the training phase, the Mel-scale Frequency Cepstral Coefficients (MFCC) were analyzed from audio signals and the Facial Animation Parameters (FAP) were extracted from video signals. Then both audio and video features were integrated to train a single HMM. In the synthesis phase, the HMM was used to correlate a completely novel audio track to a FAP sequence for face synthesis with the help of Facial Animation Engine (FAE). The experiments demonstrated the effects of the proposed voice-driven talking head on both man and woman, with two kinds of styles (speaking and singing) and using three kinds of languages (Chinese, English and Taiwanese). The possible applications of the proposed system are computer aided instruction, online guide, virtual conference, lip synchronization, human computer interaction and so on.

An efficient structure-aware bilateral texture filtering for image smoothing

Photos contain well‐structured and plentiful visual information. Edges are active and expressive stimuli for human visual perception. However, it is hard to separate structure from details because edge strength and object scale are entirely different concepts. This paper proposes a structure‐aware bilateral texture algorithm to remove texture patterns and preserve structures. Our proposed method is simple and fast, as well as effective in removing textures. Instead of patch shift, smaller patches represent pixels located at structure edges, and original patches represent the texture regions. Specifically, this paper also improves joint bilateral filter to preserve small structures. Moreover, a windowed inherent variation is adapted to distinguish textures and structures for detecting structure edges. Finally, the proposed method produces excellent experimental results. These results are compared to some results of previous studies. Besides, structure‐preserving filtering is a critical operation in many image processing applications. Our proposed filter is also demonstrated in many attractive applications, such as seam carving, detail enhancement, artistic rendering, etc.

Inner engraving for the creation of a balanced LEGO sculpture

LEGO is a globally popular toy composed of colorful interlocking plastic bricks that can be assembled in many ways; however, this special feature makes designing a LEGO sculpture particularly challenging. Building a stable sculpture is not easy for a beginner; even an experienced user requires a good deal of time to build one. This paper provides a novel approach to creating a balanced LEGO sculpture for a 3D model in any pose, using centroid adjustment and inner engraving. First, the input 3D model is transformed into a voxel data structure. Next, the model’s centroid is adjusted to an appropriate position using inner engraving to ensure that the model stands stably. A model can stand stably without any struts when the center of mass is moved to the ideal position. Third, voxels are merged into layer-by-layer brick layout assembly instructions. Finally, users will be able to build a LEGO sculpture by following these instructions. The proposed method is demonstrated with a number of LEGO sculptures and the results of the physical experiments are presented.