1. A method of correcting the position of a printed image on a printable medium, said image being generated by a computer and printed on the printable medium by a printer controlled by the computer, in which the computer executes a print operation to print an image onto a printable medium; obtains co-ordinates which define the actual position of the image printed as well as the co-ordinates of a desired position of the image; and responds to the difference between the required and the actual positions to correct the image which would be generated by the computer in the next execution of the print operation such that it will be printed at the correct position.