update unsigned char RD(int i,int j){ return (char)(_sq(cos(atan2(j-512,i-512)/2))*255); }
unsigned char GR(int i,int j){ return (char)(_sq(cos(atan2(j-512,i-512)/2-2*acos(-1)/3))*255); }
unsigned char BL(int i,int j){ return (char)(_sq(cos(atan2(j-512,i-512)/2+2*acos(-1)/3))*255);
unsigned char BL(int i,int j){ return (char)(_sq(cos(atan2(j-512,i-512)/2+2*acos(-1)/3))*255); }