The set partitioning in hierarchical trees (SPIHT) algorithm is an efficient wavelet-based progressive image-compression technique, designed to minimize the mean-squared error (MSE) between the original and decoded imagery. However, the MSE-based distortion measure is not in general well correlated with image-recognition quality, especially at low bit rates. Specifically, low-amplitude wavelet coefficients that may be important for classification are given low priority by conventional SPIHT. In this paper, we use the kernel matching pursuits (KMP) method to autonomously estimate the importance of each wavelet subband for distinguishing between different textures, with textural segmentation first performed via a hidden Markov tree. Based on subband importance determined via KMP, we scale the wavelet coefficients prior to SPIHT coding, with the goal of minimizing a Lagrangian distortion based jointly on the MSE and classification error. For comparison we consider Bayes tree-structured vector quantization (B-TSVQ), also designed to obtain a tradeoff between MSE and classification error. The performances of the original SPIHT, the modified SPIHT, and B-TSVQ are compared.

We propose an approximate Bayesian approach for unsupervised feature selection and density estimation, where the importance of the features for clustering is used as the measure for feature selection. Traditional maximum-likelihood (ML) model-parameter optimization schemes estimate the feature saliencies for a fixed model structure (i.e., a fixed number of clusters). In practice, the number of clusters present in the data for mixture-based modeling is unknown. In an ML framework, the number of clusters typically needs to be ascertained prior to estimating the feature saliencies. We propose a density estimation scheme that addresses model complexity (number of clusters present) and model-parameter estimation (feature saliencies) in a single optimization framework. The approximate Bayesian approach presented here, based on the expectation propagation method, obtains a full posterior distribution on the saliency of the features, along with full posterior distribution of other model parameters (including the number of clusters) that represent the underlying statistics of the data. The performance of the algorithm, is analyzed based on its ability to identify the features salient for clustering the multivariate data.

This paper discusses the efficient compression of images to improve the classification associated with the decoded imagery. The set partitioning in hierarchical trees (SPIHT) algorithm, an efficient wavelet-based progressive image-compression scheme, was originally designed to minimize the mean-squared error (MSE) between the original and decoded imagery. The image is first segmented at the encoder by an unsupervised method using a hidden Markov tree (HMT) mixture model in the wavelet domain. By using the kernel matching pursuits (KMP) method the recognition importance of each wavelet subband is estimated. By comparison using synthesized data, the compression and classification performance of the modified SPIHT algorithm is comparable to Bayes TSVQ, along with the advantages of fast speed and no requirement of codebook design and possibly transmission.

The Set Partitioning In Hierarchical Trees (SPIHT), an efficient wavelet-based progressive image-compression scheme, is oriented to minimize the mean-squared error (MSE) between the original and decoded imagery. In this paper, we use the kernel matching pursuits (KMP) method to estimate the importance of each wavelet sub-band for distinguishing between different textures segmented by an HMT mixture model. Before the SPIHT coding, we weight the wavelet coefficients, with the goal of achieving improved image-classification results at low bit rates. A modified SPIHT algorithm is proposed to improve the coding efficiency. The performance of the original SPIHT and the modified SPIHT algorithms is compared.

A target recognition classifier for forward-looking infrared (FUR) imagery is developed. A target class is defined as a set of contiguous target-sensor orientations (aspects) for which the associated FLIR imagery is stationary. We designed four sets of templates for each target class, to represent the overall image as well as three class-dependent subcomponents. The templates are designed by using expansion matching (EXM) filters and the Karhunen-Loeve transform (KLT). The feature vectors obtained with these eigen templates are used in the context of a support vector machine (SVM). The performance of the SVM classifier is presented and compared with other competitive classifiers.