1. A color processing method of determining saturation compression based on a visual characteristic, comprising using a color processing apparatus to perform the steps of: calculating first and second boundary points, wherein the first boundary point is an intersection point of a line passing a sample point in a source gamut and a boundary of the source gamut, and the second boundary point is an intersection point of the line and a boundary of a destination gamut; calculating a saturation difference ΔCmax from saturation C 1 of the first boundary point and saturation C 2 of the second boundary point by 
 Δ C max=√{( C 1− C 2)/(1+0.045 C* )} 2 ; calculating a saturation difference ΔCin from saturation Cin of the sample point, the saturation C 1 of the first boundary point, and the saturation difference ΔCmax by 
 Δ C in=Δ C max· C in/ C 1; and calculating a corrected saturation Cout of the sample point, to map the sample point into the destination gamut, by 
 C out=( k 2· C in−Δ C in) k 1, 
 where k 1=1+0.045/2×Δ C in, and 
 k 2=1−0.045/2×Δ C in, wherein an amount of correcting the saturation grows larger as the saturation of the sample point rises.