This invention provides an image conversion apparatus for converting a screen signal to display a converted screen signal on a monitor, with the screen signal comprising a plurality of first image signals. The image conversion apparatus comprises a format memory in which at least one data group is stored and a conversion matrix for conversion of the first image signals to a plurality of corresponding second image signals, a latch circuit electrically connected to the conversion matrix for latching the second image signals transmitted from the conversion matrix, and a control circuit electrically connected to the format memory and the latch circuit for controlling the latch circuit so that the latch circuit latches chosen second image signals, according to a lock signal in the data group transferred from the format memory.