SPRNet: Single-Pixel Reconstruction for One-Stage Instance Segmentation.

Object instance segmentation is one of the most fundamental but challenging tasks in computer vision, and it requires the pixel-level image understanding. Most existing approaches address this problem by adding a mask prediction branch to a two-stage object detector with the region proposal network (RPN). Although producing good segmentation results, the efficiency of these two-stage approaches is far from satisfactory, restricting their applicability in practice. In this article, we propose a one-stage framework, single-pixel reconstruction net (SPRNet), which performs efficient instance segmentation by introducing a single-pixel reconstruction (SPR) branch to off-the-shelf one-stage detectors. The added SPR branch reconstructs the pixel-level mask from every single pixel in the convolution feature map directly. Using the same ResNet-50 backbone, SPRNet achieves comparable mask AP with Mask R-CNN at a higher inference speed and gains all-round improvements on box AP at every scale compared with RetinaNet.