A partial region on a screen can be selected for highlighting. Information related to the partial region is transmitted from a computer to a computer monitor. In one embodiment, the partial region information is sent over a different port from the one used to send video data. The image processor adjusts contrast and sharpness of the partial region according to the partial region information. Adjustments are made for differences in a coordinate system between the computer site and the display device. The partial region can be selected from the computer or from a user interface on the computer monitor. Selected partial regions can be moved in conjunction with movements of windows containing the image. Highlighted selected regions can also be automatically disabled when the window is deactivated.