A printing system includes a media transport system configured to pick a sheet of media from a media supply and transport it along a media transport path to a printing module. An image capture system positioned along the media transport path, includes an image capture device positioned to capture a digital image of the sheet of media, and a platen positioned behind the sheet of media, wherein a surface of the platen includes a non-uniform density pattern, and wherein the captured digital image includes at least one edge of the sheet of media and a portion of the platen that extends beyond the edge of the sheet of media. An image analysis system automatically analyzes the captured digital image to detect an edge position of the sheet of media by detecting a platen region that includes the non-uniform density pattern and a media region.