An improved user interface for use with systems that display images. The interface allows easy control over the appearance of images. The user interface allows motion of a single input device to control at least two parameters of an image mapping. The controls impact the appearance of the image in real time. An operator may use the interface to optimize the appearance of a region of the image. The invention is described in connection with a contraband detection system that includes a touch screen input device. Images formed by the inspection systems are mapped to a display, with parameters provided through the touch screen controlling the mapping. The interface is employed to control the contrast of the image displayed for the operator. The value of one parameter obtained through the interface controls an intensity level at which the contrast mapping is nonlinear. The value of the second parameter obtained through the interface controls the amount of the nonlinearity.
