基于BP神经网络的人脸检测AbaBoost算法

人脸检测在日常生产和应用非常重要。本文提出了一种基于BP神经网络的AdaBoost人脸检测算法。首先,使用BP神经网络代替YCbCr高斯模型建立肤色模型。同时,针对AdaBoost算法提出了一种新的权值更新方法。在权值更新中引入阈值与样本之间的距离。另外权重有一个边界值。最后,利用BP神经网络提取图像中的肤色候选区域,并采用改进的AdaBoost算法对图像中的人脸进行精确检测。实验结果表明,利用BP神经网络和改进的AdaBoost算法的新的解决方案比现有的方法具有更高的精度。     

Histogram feature-based Fisher linear discriminant for face detection

The face pattern is described by pairs of template-based histogram and Fisher projection orientation under the framework of AdaBoost learning in this paper. We assume that a set of templates are available first. To avoid making strong assumptions about distributional structure while still retaining good properties for estimation, the classical statistical model, histogram, is used to summarize the response of each template. By introducing a novel “Integral Histogram Image”, we can compute histogram rapidly. Then, we turn to Fisher linear discriminant for each template to project histogram from d-dimensional subspace to one-dimensional subspace. Best features, used to describe face pattern, are selected by AdaBoost learning. The results of experiments demonstrate that the selected features are much more powerful to represent the face pattern than the simple rectangle features used by Viola and Jones and some variants.     

Optimization of a training set for more robust face detection

The performance of a learning-based method highly depends on the quality of a training set. However, it is very challenging to collect an efficient and effective training set for training a good classifier, because of the high dimensionality of the feature space and the complexity of decision boundaries. In this research, we study the methodology of automatically obtaining an optimal training set for robust face detection by resampling the collected training set. We propose a genetic algorithm (GA) and manifold-based method to resample a given training set for more robust face detection. The motivations behind lie in two folds: (1) dynamic optimization, diversity, and consistency of the training samples are cultivated by the evolutionary nature of GA and (2) the desirable non-linearity of the training set is preserved by using the manifold-based resampling. We demonstrate the effectiveness of the proposed method through experiments and comparisons to other existing face detectors. The system trained from the training set by the proposed method has achieved 90.73% accuracy with no false alarm on MIT+CMU frontal face test set—the best result reported so far to our knowledge. Moreover, as a fully automatic technology, the proposed method can significantly facilitate the preparation of training sets for obtaining well-performed object detection systems in different applications.     

Efficient face candidates selector for face detection

In this paper an efficient face candidates selector is proposed for face detection tasks in still gray level images. The proposed method acts as a selective attentional mechanism. Eye-analogue segments at a given scale are discovered by finding regions which are roughly as large as real eyes and are darker than their neighborhoods. Then a pair of eye-analogue segments are hypothesized to be eyes in a face and combined into a face candidate if their placement is consistent with the anthropological characteristic of human eyes. The proposed method is robust in that it can deal with illumination changes and moderate rotations. A subset of the FERET data set and the BioID face database are used to evaluate the proposed method. The proposed face candidates selector is successful in 98.75% and 98.6% cases, respectively.     

Face detection with boosted Gaussian features

Detecting faces in images is a key step in numerous computer vision applications, such as face recognition or facial expression analysis. Automatic face detection is a difficult task because of the large face intra-class variability which is due to the important influence of the environmental conditions on the face appearance. We propose new features based on anisotropic Gaussian filters for detecting frontal faces in complex images. The performances of our face detector based on these new features have been evaluated on reference test sets, and clearly show improvements compared to the state-of-the-art.     

Automatical detection of face features and exact face contour

The approach based on the mathematical morphology and the variational calculus is presented for the detection of an exact face contour in still grayscale images. The facial features (eyes and lips) are detected by using the mathematical morphology and the heuristic rules. Using these features an image is filtered and an edge map is prepared. The face contour is detected by minimizing its internal and external energy. The internal energy is defined by the contour tension and the rigidity. The external energy is defined by using the generalized gradient vector flow field of the image edge map. Initial contour is calculated using the detected face features. The contour detection experiments were performed using the database of 427 face images. Automatically detected contours were compared with manually labeled contours using an area and the Euclidean distance-based error measures.     

基于AdaBoost算法的彩色图像人脸检测研究

在彩色图像中,不同的颜色所对应的灰度值可能相同,因此在灰度图像中检测不到的信息可能在彩色图像中被检测到。本文提出一种彩色积分图概念,在AdaBoost算法的分类器训练过程中分别得到彩色图像的人脸信息,并在分类器的后五层使用融合彩色信息的分类器分类。实验表明,本文方法增强了分类器的分类能力,提高了系统的正确检测率,降低了错误报警率。     

Region-based face detection

Face detection is a challenging task. Several approaches have been proposed for face detection. Some approaches are only good for one face per image, while others can detect multiple faces from an image with greater price to pay in terms of training. In this paper, we present an approach that can be used for single or multiple face detection from simple or cluttered scenes. Faces with different sizes located in any part of an image can be detected using this approach. Three test sets are used to evaluate the system. The system has a detection rate of 100% on test set A containing 200 good quality images (200 faces) with simple backgrounds. Test set B contains 23 images (149 faces) with cluttered backgrounds and a mixture of high- and low-quality images. A detection rate of 66.4% is obtained on this set. Test set C is a selection of 22 high-quality images (54 faces) images from different sources including the World Wide Web, and a detection rate of 90.7% is obtained.     

快速人脸检测系统的设计与实现

为了快速而准确地在复杂背景的灰度或彩色图像中检测人脸,对实时人脸检测方法做了一些扩展并根据该方法设计实现了一个快速人脸检测系统,系统分为训练和检测两部分,训练方法为AdaBoost算法。测试表明该系统的性能较好。     

Automatic extraction of face contours in images and videos

The paper proposed an automatic and accurate extraction of the human face contour algorithm. Because a human face contour includes very important facial features to identifying or verifying a person, the accuracy of face contour extraction influences performance of face recognition. The automatic extraction human face contour algorithm includes a novel flowchart for improving accuracy of face contours extraction. To obtain the edge map of a face contour, the divided-and-conquer technique and Canny edge detector were used to avoid the features in the central part of face. The genetic algorithm is implemented to automatically find the parameters of Canny edge detector. Finally, the Poisson gradient vector flow (PGVF) active contour model used the edge map to extract face contours. Three datasets with temporal sequence images were tested for evaluation of the proposed algorithm. The experimental results demonstrated that the algorithm obtained accurate face contours.     

多阈值划分的连续AdaBoost人脸检测

连续AdaBoost算法要求对样本空间进行划分,传统的等距划分无法体现正负样本各自的分布规律.对基于连续AdaBoost算法的人脸检测方法进行了改进,结合离散AdaBoost中弱分类器的阈值选取策略,通过多重最优阈值选择方法实现了样本空间的合理划分.在MIT-CBCL数据库上的实验结果表明,改进后的方法比等距划分和连续AdaBoost算法检测率提高0.5%和2%,错误率降低0.15%和0.27%,算法收敛速度更快.     

Gradient feature extraction for classification-based face detection

Face detection from cluttered images is challenging due to the wide variability of face appearances and the complexity of image backgrounds. This paper proposes a classification-based method for locating frontal faces in cluttered images. To improve the detection performance, we extract gradient direction features from local window images as the input of the underlying two-class classifier. The gradient direction representation provides better discrimination ability than the image intensity, and we show that the combination of gradient directionality and intensity outperforms the gradient feature alone. The underlying classifier is a polynomial neural network (PNN) on a reduced feature subspace learned by principal component analysis (PCA). The incorporation of the residual of subspace projection into the PNN was shown to improve the classification performance. The classifier is trained on samples of face and non-face images to discriminate between the two classes. The superior detection performance of the proposed method is justified in experiments on a large number of images.     

基于肤色和AdaBoost算法的彩色人脸图像检测

针对肤色检测对复杂背景下的图像误检率高和AdaBoost算法对多姿态、多人脸图像检测效果不理想的问题,将基于肤色的人脸检测与基于AdaBoost算法的人脸检测结合起来,提出一种新的人脸检测方法,即首先利用肤色和形态学操作分割肤色区域,再根据人脸区域的统计特性筛选出人脸候选区域,然后用AdaBoost级联分类器对候选区域扫描,以精确定位人脸.实验表明,该方法同时具有肤色检测正确率高与AdaBoost算法误检率低的优点,可以有效地运用于多姿态、多人脸和复杂背景的情况,具有较好的检测效果.     

A multi-expert approach for robust face detection

Both detection accuracy and speed are of major concerns in developing a robust face detection system for real-world applications. To this end, we propose a robust face detection approach by combining multiple experts in both cascade and parallel manner. We design three detection experts which employ different feature representation schemes of local images: 2D Haar wavelet, gradient direction, and Gabor filter. The three features are classified using the same classification model, namely, a polynomial neural network (PNN) on reduced feature subspace. The detection experts are used in multiple stages with simple ones in proceeding stages and complex ones in succeeding stages for improving detection speed. Meanwhile, the output of each expert is combined with the outputs of its preceding experts to improve detection accuracy. The effectiveness of the multi-expert approach has been demonstrated in experiments on a large number of images. The obtained detection results are superior to the best individual expert and state-of-the-art approaches while the detection speed is fast.     

一种嵌入式环境下的实时人脸跟踪方法

针对复杂背景和光照变化条件下的人脸跟踪问题,提出了一种适于嵌入式环境的实时人脸跟踪方法。该方法使用帧差法检测出运动区域,在运动区域内进行AdaBoost人脸检测并进而提取人脸特征点,运用距离约束的金字塔形Lucas-Kanade方法跟踪人脸特征点。当特征点丢失较严重时,重新选取特征点进行跟踪。实验结果表明,该方法有较鲁棒的跟踪性能,在嵌入式环境下能够实时跟踪人脸。     

AdaBoost算法在人脸检测中的应用

AdaBoost方法是目前较流行的一种图像检测方法．它是基于统计模型的检测方法。针对目前一些人脸检测方法误检率高、检测速度慢的问题,详细介绍AdaBoost算法的基本原理,并应用OpenCV程序的开发．实现检测速度快、检测率和鲁棒性高的人脸检测。     

AdaBoost算法在人脸检测中的应用

AdaBoost方法是目前较流行的一种图像检测方法,它是基于统计模型的检测方法。针对目前一些人脸检测方法误检率高、检测速度慢的问题,详细介绍AdaBoost算法的基本原理,并应用OpenCV程序的开发,实现检测速度快、检测率和鲁棒性高的人脸检测。     

改进的基于AdaBoost算法的人脸检测方法*

针对传统AdaBoost算法的不足,分析了训练过程中出现的退化问题及样本权重扭曲的现象,并提出了解决这一问题的有效方法.该方法对样本权重的更新规则进行了适当的调整,即为每一轮循环设定一个权重更新阈值,根据样本是否被错误分类以及当前权重是否大于该阈值来更新样本权重,从而限制了困难样本权重的过分增大.使用该方法训练级联人脸检测器,试验结果表明,该方法较好地解决了传统AdaBoost算法所出现的退化问题,在保证检测率的同时降低了误检率.     

AdaBoost人脸检测算法在DSP上的移植与优化

将Viola等人提出的AdaBoost人脸检测算法由PC机移植到TMS320DM642嵌入式平台,采用EMCV （Embedded Computer Vision Library）移植方案,将PC平台的OpenCV（Open Source Computer Vision Library）视觉库中有关AdaBoost算法的模块修改使之适应嵌入式DSP平台。该移植工作主要解决了OpenCV在嵌入式平台的不兼容问题以及不同体系架构的编译器环境和库文件导致的编译和链接错误。优化工作在TI的编译器CCS中进行,在编译器平台下进行C语言的项目及程序优化,并进行了大量实验数据的对比,给出了优化的方案,对实现系统的实时性有指导性作用。     

一种复杂背景下的人脸检测方法

针对在复杂背景下现有人脸检测算法存在检测率低和误检率高等问题,提出了一种基于改进AdaBoost算法和肤色校验相结合的彩色图像人脸检测方法.首先对传统AdaBoost算法进行了改进,通过改进样本权值参数和弱分类器加权参数,有效地抑制了困难样本权值的过分增大,加强了分类器对样本的识别能力,并提高了系统的检测率;然后将Ad...