The objective of the present invention is to enhance a specific color
without changing the hue of an original image.At least two different
gray-level correction functions are provided for luminance signals input
for three colors, R, G and B, and these functions are used to calculate
correction coefficients for the individual colors. Then, the luminance
signals input for the three colors are synthesized so that the weighting
of the colors is changed in accordance with the input luminance signals,
and a correction coefficient is calculated that is used in common. The
input signals are then multiplied by the thus obtained correction
coefficient.