International audience

Discriminant analysis, especially Fisherface and its numerous variants, have achieved great success in face recognition. However, these methods fail to work for face recognition from Single Sample per Person (SSPP), since they need more than one sample per person to estimate the within-class scatter matrix. To break this inability of traditional discriminant analysis, our paper proposes Adaptive Discriminant Analysis (ADA). In our method, the within-class scatter matrix of each enrolled subject is estimated from his/her single sample, by inferring from a generic training set with multiple samples per person. The inference is inspired by a simple intuition that similar person follows similar within-class variations. Specifically, both kNN regression and Lasso regression are explored for this purpose. We evaluate our method on FERET database and a large real-world face database. The results are very impressive compared with dominant traditional solutions to SSPP problem.

This paper presents a novel schema to address the polysemy of visual words in the widely used bag-of-words model. As a visual word may have multiple meanings, we show it is possible to use semantic contexts to disambiguate these meanings and therefore improve the performance of bag-of-words model. On one hand, for an image, multiple context-specific bag-of-words histograms are constructed, each of which corresponds to a semantic context. Then these histograms are merged by selecting only the most discriminative context for each visual word, resulting in a compact image representation. On the other hand, an image is represented by the occurrence probabilities of semantic contexts. Finally, when classifying an image, two image representations are combined at decision level to utilize the complementary information embedded in them. Experiments on three challenging image databases (PASCAL VOC 2007, Scene-15 and MSRCv2) show that our method significantly outperforms state-of-the-art classification methods.

Fisher's linear discriminant (FLD) is one of the most widely used linear feature extraction method, especially in many visual computation tasks. Based on the analysis on several limitations of the traditional FLD, this paper attempts to propose a new computational paradigm for discriminative linear feature extraction, named "classifiability-based discriminatory projection pursuit" (CDPP), which is different from the traditional FLD and its variants. There are two steps in the proposed CDPP: one is the construction of a candidate projection set (CPS), and the other is the pursuit of discriminatory projections. Specifically, in the former step, candidate projections are generated by using the nearest between-class boundary samples, while the latter is efficiently achieved by classifiability-based AdaBoost learning from the CPS. We show that the new "projection pursuit" paradigm not only does not suffer from the limitations of the traditional FLD but also inherits good generalizability from the boundary attribute of candidate projections. Extensive experiments on both synthetic and real datasets validate the effectiveness of CDPP for discriminative linear feature extraction.

This paper shows how semantic attribute features can be used to improve object classification performance. The semantic attributes used fall into five groups: scene (e.g. ‘road’), colour (e.g. ‘green’), part (e.g. ‘face’), shape (e.g. ‘box’), and material (e.g. ‘wood’). We train classifiers from representative images for 60 semantic attributes. We first assess the accuracy of the individual classifiers, and show that they can be used to predict semantic annotations for test images. We then use output from the set of trained classifiers to create a new low-dimensional image representation. Experiments on data from the PASCAL VOC challenge show that the semantic attribute features achieve an object classification performance close to that of high-dimensional bag-of-words features, and that using a combination of semantic attribute features and bag-of-words features gives a better classification performance than using either feature set alone.