Box Refinement: Object Proposal Enhancement and Pruning

Object proposal generation has been an important preprocessing step for object detectors in general and the convolutional neural network (CNN) detectors in particular. Recently, people start to use the CNN to generate object proposals but most of these methods suffer from the localization bias problem, like other objectness-based methods. Since contours offer a powerful cue for accurate localization, we propose a box refinement method by searching for the optimal contour for each initial bounding box that minimizes the contour cost. Experiments on the PASCAL VOC2007 test dataset show that our box refinement method can significantly improve the object recall at a high overlapping threshold while maintaining a similar recall at a loose one. Given 1000 proposals, the average recall of multiple existing methods is increased by more than 5% with our box refinement process integrated.