1. A screen image converter comprising: a number array supplier for storing a number array and outputting the number array; an image converter for converting the screen image by calculating converted digital screen image data with the number array from the number array supplier; and a memory storage for storing the converted image data calculated by the image converter and outputting the converted image to an exterior; wherein the number array supplier has from first to Nth numerical sequences (N is an integer larger than 1) constituting a number array of n×m (n and m are integers equal to or larger than 1), the image converter receives an Mth inputted image (Mε{1,. .. , N}) of number array of n×m, and receives an Mth inputted number array from the number array supplier, records an Mth conversion result generated by calculating the Mth inputted image and the Mth inputted number array in the image storage, and outputs the converted result from the memory storage successively.