Patent ID: 6917707

Claim:
An image processing method for density correction of a digital image by converting input analog image signals into digital image signals, generating a pixel density histogram from the digital image and making density correction of the digital image based on the generated density histogram, wherein, for the density histogram, the first threshold representing the threshold density for the background, the second density threshold representing the minimum frequency for the background density value, the third threshold density value for the maximum density and the fourth threshold representing the minimum frequency for the maximum density have been set beforehand, the image processing method comprising the steps of: from the total density range of the density histogram, defining as the background density determination area the range having the density values determined based on the first threshold and having a frequency equal to or greater than the second threshold and defining as the maximum density determination area the range having the density values determined based on the third threshold and having a frequency equal to or greater than the fourth threshold; determining as the background density a density class which is closest to the first threshold, of all the density classes which belong to the background density determination area; determining as the maximum density a density class which is farthest from the third threshold, all of the density classes which belong to the maximum density determination area; and performing density correction based on the density classes of the background and the maximum density.