JPS6423680A - Image input device - Google Patents

Abstract

PURPOSE:To prevent a density from being changed in the same color part of a half tone image such as a photograph in an output image by changing a time constant used for detecting an envelope, changing the quantity of a shading correction and changing a comparing level according to that the image is the simple binary image or the half tone image. CONSTITUTION:A CCD 25 for irradiating a light on the image and changing the reflected light to an electric signal, a circuit for detecting the envelope of a video signal outputted from this CCD 25 and correcting a shading and a comparator 125 for binarizing the video signal are provided. Then, the quantity of the correction of the shading suitable respectively for a character, the photograph is changed by changing the time constant for detecting the envelope or the like according to that the image is the character or the photograph and the comparing level of a binarization is changed. Thereby, at the time of representing the character and the photograph, namely, at the time of representing a simple binary and a pseudo binary (or half tone), in the case of the character, the black and white of an output image is cleared and in case of the photograph, the output image similar to an input image as much as possible can be obtained.