Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Machine Graphics and Vision

2 2006

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Toward robust face analysis method of non-cooperative persons in stereo color image sequences

Al-Hamadi A. K., Niese R., Panning A., Michaelis B.

Machine Graphics and Vision

2006

Vol. 15, No. 3/4

245-254

This paper describes a novel method for analyzing single faces of non-cooperative persons on the basis of stereoscopic color images. The challenges arise from the fact that the persons observed are non-cooperative, which in turn complicates further processing as facial feature extraction and tracking in image sequence. In our method, face detection is based on color-driven clustering of 3D points derived from stereo. A mesh model is registered with a post-processed face cluster, using a variant of the Iterative Closest Point algorithm [ICP]. The pose is derived from correspondence. Then, the pose and model information are used for face normalization and facial feature localization. Automatic extraction of facial features is carried out using modified Active Shape Models [ASM]. In contrast to the simple ASM, another approach is pursued in this work. It involves two modifications to the ASM, which lead to greater stability and robustness. The results show that stereo and color are powerful cues for finding the face and its pose, and for facial feature extraction under a wide range of poses, illumination types and expressions [PIE].

Dense depth map reconstruction by phase difference-based algorithm under influence of perspective distortion

El-Etriby S., Al-Hamadi A., Michaelis B.

Machine Graphics and Vision

2006

Vol. 15, No. 3/4

349-361

This paper describes a novel phase difference-based algorithm applied to the corresponding points in two views, which takes into account the surface perspective distortion (foreshortening). The challenges arise from the fact that stereo images are acquired from slightly different views. Therefore, the surface of a projected image is more compressed and occupies a smaller area in one view. Since the projective distortion region can not be estimated in terms of a fixed-size matching algorithm, we suggest using a local spatial frequency representation model to address this problem. Instead of matching intensities directly, a Gabor scale-space expansion (scalogram) is used. The scalogram expresses the filter output as a function of the spatial position and the principal wavelength to which the filter is tuned. The phase difference at the corresponding points in the two images is used to find the disparity value. The suggested algorithm provides an analytical closed-form expression for the perspective foreshortening effect. The foreshortening factor is verified to overcome the perspective distortion region. The efficiency and performance of the suggested algorithm for dense depth map reconstruction is demonstrated on the basis of analysis of rectified real images. Hence, our proposed method has a superior performance in comparison with other conventional methods.