Zujun Hou

Residual orientation modeling for fingerprint enhancement and singular point detection

This paper presents a novel method for fingerprint orientation modeling, which executes in two phases. Firstly, the orientation field is reconstructed using a lower order Legendre polynomial to capture the global orientation pattern in the fingerprint structure. Then the preliminary model around the region with presence of fingerprint singularities is dynamically refined using a higher order Legendre polynomial. The singular region is automatically detected through the analysis on the orientation residual field between the original orientation field and the orientation model. The method does not require any prior knowledge on the fingerprint structure. To validate the performance, the method has been applied to fingerprint image enhancement, fingerprint singularity detection and fingerprint recognition using the FVC 2004 data sets. Compared with the recently published Legendre polynomial model, the proposed method attains higher accuracy in fingerprint singularity detection, lower error rates in fingerprint matching.

A review on fingerprint orientation estimation

Fingerprint orientation plays important roles in fingerprint enhancement, fingerprint classification, and fingerprint recognition. This paper critically reviews the primary advances on fingerprint orientation estimation. Advantages and limitations of existing methods have been addressed. Issues on future development have been discussed. Copyright

Keypoint-based near-duplicate images detection using affine invariant feature and color matching

This paper presents a new keypoint-based approach to near-duplicate images detection. It consists of three steps. Firstly, the keypoints of images are extracted and then matched. Secondly, the matched keypoints are voted for estimation of affine transform based on an affine invariant ratio of normalized lengths. Finally, to further confirm the matching, the color histograms of areas formed by matched keypoints in two images are compared. This method has the advantage for handling the case when there are only a few matched keypoints. The proposed algorithm has been tested on Columbia dataset and conducted the quantitative comparison with RANdom SAmple Consensus (RANSAC) algorithm and Scale-Rotation Invariant Pattern Entropy (SR-PE) algorithm. The experiment result turns out that the proposed method compares favorably against the state-of-the-arts.

Visible Entropy: A Measure for Image Visibility

Image visibility is a fundamental issue in the field of computer vision. This paper investigates the connection between histogram and image visibility, where the concept of entropy is employed to depict the information content of the histogram. It turns out that image visibility is more dependent on the observed intensity levels with higher frequencies and the distribution of their locations in the range of intensity levels. With this in mind, the concept of visible entropy is proposed. The usefulness of the proposed visibility measure has been evaluated using a number of realistic images.

Automatic nipple detection using shape and statistical skin color information

This paper presents a new approach on nipple detection for adult content recognition, it combines the advantage of Adaboost algorithm that is rapid speed in object detection and the robustness of nipple features for adaptive nipple detection. This method first locates the potential nipple-like region by using Adaboost algorithm for fast processing speed. It is followed by a nipple detection using the information of shape and skin color relation between nipple and non-nipple region. As this method uses the nipple features to conduct the adult image detection, it can achieve more precise detection and avoids other methods that only detect the percentage of exposure skin area to decide whether it is an adult image. The proposed method can be also used for other organ level detection. The experiments show that our method performs well for nipple detection in adult images.

Combination of local and global features for near-duplicate detection

This paper presents a new method to combine local and global features for near-duplicate images detection. It mainly consists of three steps. Firstly, the keypoints of images are extracted and preliminarily matched. Secondly, the matched keypoints are voted for estimation of affine transform to reduce false matching keypoints. Finally, to further confirm the matching, the Local Binary Pattern (LBP) and color histograms of areas formed by matched keypoints in two images are compared. This method has the advantage for handling the case when there are only a few matched keypoints. The proposed algorithm has been tested on Columbia dataset and compared quantitatively with the RANdom SAmple Consensus (RANSAC) and the Scale-Rotation Invariant Pattern Entropy (SR-PE) methods. The results turn out that the proposed method compares favorably against the state-of-the-arts.

A Variational Formulation for Fingerprint Orientation Modeling

Fingerprint orientation plays important roles in fingerprint recognition. This paper proposes a framework for modeling the fingerprint orientation field based on the variational principle. The proposed method does not require any prior information about the structure of acquired fingerprints. Comparison has been made with respect to state-of-the-arts in fingerprint orientation modeling.

A variational formulation for fingerprint orientation modeling

Orientation pattern is an important feature for characterizing fingerprint and plays critical roles in fingerprint recognition and fingerprint classification. This paper proposes a framework for modeling the fingerprint orientation field based on the variational principle, where the orientation pattern can be estimated through solving the associated Euler-Lagrange equation. Compared with existing methods, our proposed method has the following features. Firstly, it does not require any prior information about the structure of the acquired fingerprint, such as location of singular point(s). Secondly, it explicitly provides freedom for modeling the singularity in the orientation field. Thirdly, it has less number of parameters. Comparison has been made with respect to state-of-the-arts in fingerprint orientation modeling in terms of modeling accuracy, fingerprint enhancement and singular point detection. Advantages of the proposed method are demonstrated.

A systematic topological method for fingerprint singular point detection

Singular point detection is an important issue in fingerprint image analysis. General methods like Poincare index method can detect singular points in non-arch type fingerprints but fail on arch-type fingerprints. Some more sophisticated methods like complex filter method also face the same problem. In this paper, we propose a systematic method for detecting singular points in fingerprint images which utilizes the most fundamental topological feature of acquired fingerprints as the basis for singular point identification. The method differentiates the input fingerprint between arch type and non-arch type. For non-arch type fingerprints singular points are detected as intersection points in a c(>2) level segmentation map. As for arch type fingerprints, singular points are identified from the symmetric line of the fingerprint structure. The method is evaluated using the NIST DB4 database and compared with the complex filter method. The proposed method attains near 90% success rate in detecting singular points and the displacement from ground truth is comparable to that of the complex filter method. Moreover our method is more than once faster in CPU time.

Object boundary extraction using Active B-Snake Model

A new deformable model called active b-snake model (ABM) is presented for object boundary extraction. First, an affine-invariant landmark point assignment strategy is proposed to avoid manually assign landmarks. Second, an adaptive control point insertion algorithm is used to enhance the flexibility of B-Snake to describe complex shape. Third, for modeling the shape distribution and appearance characteristics of landmark points in the training samples, a statistical framework is embedded into ABM. Finally, the minimum mean square error (MMSE) approach with control point insertion provides fine deformation to the desired object boundaries. Experimental results show that ABM can be used to achieve more accurate object extraction.