Patent ID: 7809205

Claim:
An image processing method in which image data is transformed to spatial frequencies to obtain multiple frequency components, the obtained frequency components are processed, the processed frequency components are inversely transformed to image data, and the number of gray levels of the inversely transformed image data is decreased, comprising the steps of: comparing the absolute value of each of specific multiple frequency components in the multiple frequency components obtained after transformation to spatial frequencies with a predetermined value in terms of magnitude; changing each of said specific frequency components on the basis of the result of the comparison; adding a specific value to each of said specific frequency components having been changed and other frequency components; and inversely transforming the frequency components, to which the specific values have been added, to image data, wherein said specific frequency components in all frequency components are the frequency components on the low frequency side and the frequency components on the high frequency side only in the horizontal direction and the frequency components on the high frequency side only in the vertical direction of image data, in the case that the absolute value of the coefficient of each of said specific frequency components is larger than said predetermined value, the coefficient of said frequency component is increased.