| 摘要 |
PURPOSE:To execute an exact image processing, while saving its resolution even to a low contrast character part by standardizing a difference between the maximum value and the minimum value by a mean value, comparing its standard value with a prescribed reference value and identifying whether image information is a binary image or not. CONSTITUTION:The output of a dynamic threshold level calculating circuit 33 where the maximum image density Dmax and the minimum image density Dmin are inputted from a maximum value/minimum value detecting circuit 42 is connected to a first threshold level generating circuit 5, and when the picture element concerned is decided to be a character image element, a threshold level Bh at the time of bringing the image element concerned to simple binarization is calculated. The second threshold level generating circuit 6 generates a binarization threshold level of a photograph part and outputs a dither threshold level as the second threshold level signal 15b to a selecting circuit 8. The selecting circuit 8 determines a selective threshold level signal 16 as a discriminating signal 12 control signal from the first and the second threshold level signals 15a, 15b. A comparator 9 compares the selective threshold level signal 16 and the image signal 17 of the image element concerned supplied through a delaying circuit 10, and outputs an output image signal 18. |
