Early Hierarchical Contexts Learned by Convolutional Networks for Image Segmentation

We propose a foreground segmentation method based on convolutional networks. To predict the label of a pixel in an image, the model takes a hierarchical context as the input, which is obtained by combining multiple context patches on different scales. Short range contexts depict the local details, while long range contexts capture the object-scene relationships in an image. Early means that we combine the context patches of a pixel into a hierarchical one before any trainable layers are learned, i.e., early-combing. In contrast, late-combing means that the combination occurs later, e.g., when the convolutional feature extractor in a network has already been learned. We find that it is vital for the whole model to jointly learn the patterns of contexts on different scales in our task. Experiments show that early-combing performs better than late-combing. On the dataset1 built up by Baidu IDL2 for a latest person segmentation contest, our method beats all the competitors with a considerable margin. Qualitative results also show that the proposed method is almost ready for practical application.