Multi-Task Deep Relative Attribute Learning for Visual Urban Perception.

Visual urban perception aims to quantify perceptual attributes (e.g., safe and depressing attributes) of physical urban environment from crowd-sourced street-view images and their pairwise comparisons. It has been receiving more and more attention in computer vision for various applications, such as perceptive attribute learning and urban scene understanding. Most existing methods adopt either (i) a regression model trained using image features and ranked scores converted from pairwise comparisons for perceptual attribute prediction or (ii) a pairwise ranking algorithm to independently learn each perceptual attribute. However, the former fails to directly exploit pairwise comparisons while the latter ignores the relationship among different attributes. To address them, we propose a Multi-Task Deep Relative Attribute Learning Network (MTDRALN) to learn all the relative attributes simultaneously via multi-task Siamese networks, where each Siamese network will predict one relative attribute. Combined with deep relative attribute learning, we utilize the structured sparsity to exploit the prior from natural attribute grouping, where all the attributes are divided into different groups based on semantic relatedness in advance. As a result, MTDRALN is capable of learning all the perceptual attributes simultaneously via multi-task learning. Besides the ranking sub-network, MTDRALN further introduces the classification sub-network, and these two types of losses from two sub-networks jointly constrain parameters of the deep network to make the network learn more discriminative visual features for relative attribute learning. In addition, our network can be trained in an end-to-end way to make deep feature learning and multi-task relative attribute learning reinforce each other. Extensive experiments on the large-scale Place Pulse 2.0 dataset validate the advantage of our proposed network. Our qualitative results along with visualization of saliency maps also show that the proposed network is able to learn effective features for perceptual attributes.