Convolutional neural networks (CNNs) have achieved great success in visual recognition because of the availability of large-scale image datasets, such as the ImageNet. The transfer of convolutional features to challenging scene recognition remains an open problem. Multiple non-linear transforms endow the convolutional features with abundant information. On the other side, CNNs are adept at capturing the holistic appearances of scenes, whereas the lack of some critical local details may reduce the recognition accuracy. To address these problems, we propose a novel hierarchical coding algorithm to learn effective representations. To adapt the scale variations, many useful patches with various scales sampled from the whole image are considered to provide the sufficient details. Non-negative sparse decomposition model (NNSD) based on convolutional features is proposed to learn the sharable components for each scale and further produce global signatures. Based on the global signatures, inter-class linear coding (ICLC) is proposed to learn the discriminative components and ultimate image representations. Experimental results indicate that our approach significantly improves the recognition accuracy compared with general CNN models and achieves excellent performance on five standard benchmarks.

We have developed a very simple yet highly reliable face recognition method called the VQ histogram method. A codevector referred (or matched) count histogram, which is obtained by vector quantization (VQ) processing of the facial image, is utilized as a very effective personal feature. By applying appropriate low pass filtering and VQ processing to a facial image, useful features for face recognition can be extracted. Experimental results show a recognition rate of 95.6% for 400 images of 40 persons (10 images per person), which contain variations in lighting, pose, and expression, from the publicly available ORL database. Equal error rate (ERR) of 2.6% is obtained for the verification experiment. By combining multiple low pass filtering procedures, the recognition rate is increased to 97% or higher.