一种视觉词软直方图的图像表示方法

Visual Word Soft-Histogram for Image Representation

基于视觉词的统计建模和判别学习,提出一种视觉词软直方图的图像表示方法.假设属于同一视觉词的图像局部特征服从高斯混合分布,利用最大-最小后验伪概率判别学习方法从样本中估计该分布,计算局部特征与视觉词的相似度.累加图像中每个视觉词与对应局部特征的相似度,在全部视觉词集合上进行结果的归一化,得到图像的视觉词软直方图.讨论了两种具体实现方法:一种是基于分类的软直方图方法,该方法根据相似度最大原则建立局部特征与视觉词的对应关系;另一种是完全软直方图方法,该方法将每个局部特征匹配到所有视觉词.在数据库Caltech-4和PASCAL VOC 2006上的实验结果表明,该方法是有效的.

This paper proposes a visual word soft-histogram for image representation based on statistical modeling and discriminative learning of visual words. This type of learning uses Gaussian mixture models （GMM） to reflect the appearance variation of each visual word and employs the max-min posterior pseudo-probabilities discriminative learning method to estimate GMMs of visual words. The similarities between each visual word and corresponding local features are computed, summed, and normalized to construct a soft-histogram. This paper also discusses the implementation of two representation methods. The first one is called classification-based soft histogram, in which each local feature is assigned to only one visual word with maximum similarity. The second one is called completely soft histogram, in which each local feature is assigned to all the visual words. The experimental results of Caltech-4 and PASCAL VOC 2006 confirm the effectiveness of this method.