AWkS: adaptive, weighted k-means-based superpixels for improved saliency detection

Abstract

Clustering inspired superpixel algorithms perform a restricted partitioning of an image, where each visually coherent region containing perceptually similar pixels serves as a primitive in subsequent processing stages. Simple linear iterative clustering (SLIC) has emerged as a standard superpixel generation tool due to its exceptional performance in terms of segmentation accuracy and speed. However, SLIC applies a manually adjusted distance measure for dis-similarity computation which directly affects the quality of superpixels. In this work, self-adjustable distance measures are adapted from the weighted k-means clustering (W-k-means) for generating superpixel segmentation. In the proposed distance measures, an adaptive weight associated with each variable reflects its relevance in the clustering process. Intuitively, the variable weights correspond to the normalization terms in SLIC that affect the trade-off between superpixels boundary adherence and compactness. Weights that influence consistency in superpixel generation are automatically updated. The variable weights update is accomplished during optimization with a closed-form solution based on the current image partition. The proposed adaptive, W-k-means-based superpixels (AWkS) experimented on three benchmarks under different distance measure outperform the conventional SLIC algorithm with respect to various boundary adherence metrics. Finally, the effectiveness of the AWkS over SLIC is demonstrated for saliency detection.