Layout-free dewarping of planar document images

For user convenience, processing of document images captured by a digital camera has been attracted much attention. However, most existing processing methods require an upright image such like captured by a scanner. Therefore, we have to cancel perspective distortion of a camera-captured image before processing. Although there are rectification methods of the distortion, most of them work under certain assumptions on the layout; the borders of a document are available, textlines are in parallel, a stereo camera or a video image is required and so on. In this paper, we propose a layout-free rectification method which requires none of the above assumptions. We confirm the effectiveness of the proposed method by experiments.