An image processing method for correcting pixel values of each pixel
constituting color image data by shifting, in a coordinate system, a
mathematical correction function defining correction values for input
values. The method includes the computer-implemented steps of: (1)
determining a maximum value and a minimum value among correction values
of respective color components obtained for each pixel by using said
correction function and then calculating differences between the
respective correction values of the respective color components and said
minimum value and calculating also a difference between said maximum
value and the minimum value; (2) dividing the calculated differences
between the respective correction values of the respective color
components and the minimum value by the calculated difference between the
maximum value and the minimum value, thereby to obtain color ratios for
the respective color components; (3) judging, as an inappropriate pixel,
any pixel having a correction value overflowing from a predetermined
maximum output gradation value and setting the overflowing correction
value to the predetermined maximum output gradation value and judging
also, as an inappropriate pixel, any pixel having a correction value
underflowing from a predetermined minimum output gradation value and
setting the underflowing correction value to the predetermined minimum
output gradation value; and (4) effecting color balance adjustment so as
to cause the correction values of the inappropriate pixel to agree with
said respective color ratio thereof.