An image processing apparatus comprises a character extraction unit (12, 24) for extracting an area whose density distribution characteristic meets a predetermined condition such as a binarization threshold and a size and a type of local filtering, from an input image (11) of multiple gray levels, and extracts an object area (15a) as an output image - (13) from the input image by using the characteristic extraction unit. Area designation means (15, 25) designates an area having a uniform density distribution and containing the object area, to the input image. Condition determination means (16, 26) determines the condition for the characteristic extraction unit based on the density distribution characteristic of the input image in the designated area. In an image processing expert system, the image characteristics of the object image and the background in the area designated by the area designation means are evaluated and analyzed (227, 223, 224) and the inquiry in the form of message is effected to quantize the evaluation of the image characteristic. As a result, the area extraction procedure (222) can be easily executed by the interaciton with an operator.