62 a logical not device or step 64 and a logical and device or step 65 the shift right register or step 58 and the shift left register or step 60 are adapted to receive a scan line from the pixel map and respectively shift the scan line one digit right or left to process a particular pixel element p in the pixel map 28 using to the hardware or software scheme illustrated in fig4 the following steps are performed first the scan line 66 containing the present pixel element p is sent through the shift right register or step 58 the result of which is sent to the and device or step 62 the present scan line 56 is also sent through the shift left register or step 60 the result of which is sent to the and device or step 62 the previous scan line 68 is sent to the and device or step 62 and the subsequent scan line 70 is also sent to the and device or step 62 the logical and device 62 will produce a resultant scan line 72 next the pixel element p u2032 in the resultant scan line 72 corresponding to the position of the present pixel element p in the present scan line 68 is sent through the not device or step 64 the output of which is sent to the a input of the and device or step 65 the other input to.