METHOD FOR DISCRIMINATING DOT PHOTOGRAPHY AREA

摘要

PURPOSE:To make it possible to identify a dot area in a picture signal with a simple circuit by dividing a half tone picture signal into several number of blocks that consist of multiple picture elements and deciding whether it is a dot area or not by measuring the change of the signal level of the picture element in the block both in the direction of a main scanning and of a subscanning. CONSTITUTION:The picture element is stored at registers 31 and 32 in a prescribed order by a memory address controller 4. A difference between the picture elements inputted to the registers 31 and 32 is calculated at a subtracter 5 and the subtracted value is inputted to registers 61 and 62 in order. The signal of difference of the registers 61 and 62 detects a positive/negative change by a positive negative change detection circuit 7 and a counter selector 8 decides that the detected result is whether in the direction of the main scanning or of the subscanning by the memory address controller 4 and transmits the result of the detection to either one of counters 91 or 92. At the completion of process of one block a dot area deciding circuit 10 compares each value of counters 91 and 92 with a prescribed value and when both values are greater than the prescribed value, it outputs a signal that is the dot area to a decision result output terminal 11.