PURPOSE: To judge whether a specified picture element area is a light and shade picture or black-white picture, by obtaining the maximum occurring frequency of absolute value of density level difference between each adjoining picture element for every minute area, and detecting whether or not cases where the density level difference is 0, are more.

CONSTITUTION: Input picture element signals BS are successively read in shift registers SR1WSR32 for every picture element. Absolute values of differences between the output of picture element information successively delivered from the shift register SR1 and the output obtained by delaying the output of picture element information by one picture element at a latch circuit L are obtained by an absolute value subtractor S. Then, pulse signals are generated in accordance with the absolute value output thus obtained, and the pulse signals are given to a counter CNT. The output of the counter CNT is distributedly output to latch circuits CL1WCL54 by a multiplexer M1 corresponding to the output of another counter MC. The content output to the latch circuits CL1WCL54 and kept in them is given to a maximum frequency detecting circuit MAX through another multiplexer M2 and the maximum occurring frequency value is detected. Then, whether the value is 0 or not is detected by a comparator CMP.