Patent ID: 7113639

Claim:
An image processing method comprising the steps of: reading an original with a first reading condition to generate input image data; calculating the sharpness of said input image from said input image; discriminating whether the kind of the original is a text original or a photograph original, based on the sharpness of said input image; and applying, in case said original kind discrimination step discriminates that said original is a photograph original, a density correction process to the input image obtained by reading said original; wherein said photograph image density correction step includes: a density histogram generation step of generating a density histogram from said input image; a cumulative histogram generation step of cumulating the frequency of density level values in an increasing direction of the density level value, taking the minimum density level value of data of the density histogram obtained in said density histogram generation step as a reference and starting point of cumulating operation, thereby obtaining a cumulative histogram indicating the relationship between the density level value and the cumulative value; a first γ value obtaining step of calculating an approximation exponential function approximating said cumulative histogram and obtaining a first γ value indicating the density correction coefficient of the input image from the exponent of thus calculated function; and a first density correction step of executing a density correction process of said input image, based on said first γ value.