1. A device, comprising: an imaging subsystem for generating image data; a monitor for displaying an image; and a processor enabled for: receiving the image data; generating a reduced resolution frame based on an input frame of the image data, the reduced resolution frame comprising fewer pixels than the input frame; attempting to identify linear features defining a candidate quadrilateral form in the image data; displaying the reduced resolution frame on the monitor; and providing a user-perceptible hint in the displayed reduced resolution frame for guiding a user to alter positioning of the device to improve the device's capability for identifying linear features defining a candidate quadrilateral form in the image data.