Abstract: A computer is used to combine images by video treatment and to display the resultant image. Rather than use a frame store for storing each component image to be treated, the computer is used for storing the component images and only a single frame store is used for storing the resultant image ready for display, with a consequent saving of hardware. The image in the frame store can be refreshed either as a whole or only in the parts which have recently been edited. The images to be combined can be ordinary images or control images, the control applying control functions (such as blurring) to the image with which it is being combined.