色彩逻辑算法

这是理论上的解释

和C中的算法：

typedef struct {    unsigned char r, g, b;} RGB;double ColourDistance(RGB e1, RGB e2){    long rmean = ( (long)e1.r + (long)e2.r ) / 2;    long r = (long)e1.r - (long)e2.r;    long g = (long)e1.g - (long)e2.g;    long b = (long)e1.b - (long)e2.b;    return sqrt((((512+rmean)*r*r)>>8) + 4*g*g + (((767-rmean)*b*b)>>8));}