PROCESSING SYSTEM OF HALF TONE SIGNAL

摘要

PURPOSE:To ensure good reproduction of an original which contains characters and pictures, by separating the character pictures and pictures of variable densities by the difference of inclinations of density to secure high reproducibility of gradations. CONSTITUTION:The picture information is stored alternately in picture memories 1 and 2. The contents of the memories 1 and 2 are transferred to a block memory 3 with each block (4X4=16 picture elements). An image range deciding circuit 4 detects the maximum and minimum levels of density for each picture element within a block on the basis of the contents of the memory 3. Then the difference of these levels of density is obtained and compared with the prescribed value. Thus a character display region and a variable density display region are decided. Based on the result of this decision, a threshold value memory switching circuit 5 selects a threshold value memory 6 for variable density display region or a threshold value memory 7 for character display region and then feeds the threshold value to a signal processing circuit 8. The circuit 8 transmits a half tone signal.