All-in-one “HairNet”: A Deep Neural Model for Joint Hair Segmentation and Characterization

The hair appearance is among the most valuable soft biometric traits when performing human recognition at-a-distance. Even in degraded data, the hair's appearance is instinctively used by humans to distinguish between individuals. In this paper we propose a multi-task deep neural model capable of segmenting the hair region, while also inferring the hair color, shape and style, all from in-the-wild images. Our main contributions are two-fold: 1) the design of an all-in-one neural network, based on depthwise separable convolutions to extract the features; and 2) the use convolutional feature masking layer as an attention mechanism that enforces the analysis only within the ‘hair’ regions. In a conceptual perspective, the strength of our model is that the segmentation mask is used by the other tasks to perceive - at feature-map level - only the regions relevant to the attribute characterization task. This paradigm allows the network to analyze features from nonrectangular areas of the input data, which is particularly important, considering the irregularity of hair regions. Our experiments showed that the proposed approach reaches a hair segmentation performance comparable to the state-of-the-art, having as main advantage the fact of performing multiple levels of analysis in a single-shot paradigm.