Draw a 4X4 chessboard rotated 45˚ with the horizontal axis. Use Bresenham algorithm to draw all the lines. Use seed fill algorithm to fill black squares of the rotated chessboard

#include <GL/glut.h>
#include<math.h>
#include<stdlib.h>
#include<iostream>
#include<stdio.h>
#define PI 3.14159265/180
using namespace std;
float rtri=0.0f;
int ww=660,wh=660; 
int xi,yi,xf,yf,xx,yy;
float fillcol[3]={0.9,0.0,0.2};
float bordercol[3]={0.0,0.0,0.0};
void setpixel(int pointx,int pointy,float f[3])
{
glBegin(GL_POINTS);
glColor3f(f[0],f[1],f[2]);
glVertex2d(pointx,pointy);
glEnd();
glFlush();
}
void getpixel(int x,int y,float pixels[3])
{
glReadPixels(x,y,1.0,1.0,GL_RGB,GL_FLOAT,pixels);
}
int sign(float arg)
{
if(arg<0)
return -1;
else if(arg==0)
return 0;
else
return 1;
}
double calx(double xold,double yold,double angle)
{
double xnew;
xnew=xold*cos(PI*angle)-yold*sin(PI*angle);
return xnew;
}
double caly(double xold,double yold,double angle)
{
double ynew;
ynew=xold*sin(PI*angle)+yold*cos(PI*angle) ;
return ynew;
}
void Bre(int X1,int Y1,int X2,int Y2,double angle)
{
 double xold=0,yold=0;
 double xnew=0,ynew=0;
xold=X1;
yold=Y1;
xnew=calx(xold,yold,angle);
ynew=caly(xold,yold,angle);
X1=(int)xnew;
   Y1=(int)ynew;
xold=X2;
yold=Y2;
xnew=xold*cos(PI*angle)-yold*sin(PI*angle) ;
ynew=xold*sin(PI*angle)+yold*cos(PI*angle) ;
X2=(int)xnew;
Y2=(int)ynew;
  float dx=abs(X2-X1);
 float dy=abs(Y2-Y1);
 int s1,s2,exc,y,x,i;
  float g,temp;
x=X1;
y=Y1;
s1=sign(X2-X1);
s2=sign(Y2-Y1);
glBegin(GL_POINTS); // Plot the points
//rotate 45 on x axis
if(dy>dx)
{
temp=dx;
dx=dy;
dy=temp;
exc=1;
}
else
{
exc=0;
}
g=2*dy-dx;
i=1;
while(i<=dx)
{
glVertex2d(x,y);
while(g>=0)
{
if(exc==1)
x=x+s1;
else
y=y+s2;
g=g-2*dx;
}
if(exc==1)
y=y+s2;
else
x=x+s1;
g=g+2*dy;
i++;
}
 glEnd();
glFlush();
}
void display() 
  { 
double angle=45;
glClearColor(1.0,1.0,1.0,0); // Set Background color to white
glColor3f(0.0,0.0,0.0);
glViewport(0,0,1360,760);
glLoadIdentity();
gluOrtho2D(0 , 1360 , 0 , 760);       
glClear(GL_COLOR_BUFFER_BIT);
Bre(300,00,500,00,angle);
Bre(300,00,300,200,angle);
Bre(500,200,300,200,angle);
Bre(500,200,500,00,angle);//outer
Bre(300,50,500,50,angle);
Bre(300,100,500,100,angle);
Bre(300,150,500,150,angle);//outer
Bre(350,00,350,200,angle);
Bre(400,00,400,200,angle);
Bre(450,00,450,200,angle);//outer
angle=0;
Bre(300,00,500,00, angle);
Bre(300,00,300,200, angle);
Bre(500,200,300,200, angle);
Bre(500,200,500,00, angle);
Bre(300,50,500,50, angle);
Bre(300,100,500,100,angle);
Bre(300,150,500,150,angle);//outer
Bre(350,00,350,200, angle);
Bre(400,00,400,200, angle);
Bre(450,00,450,200, angle);//outer
}
void bfill(int x,int y,float fillcolor[3],float bordercolor[3])
{
float inter_color[3];
getpixel(x,y,inter_color);
if((inter_color[0]!=bordercolor[0]&&inter_color[1]!=bordercolor[1]&&inter_color[2]!=bordercolor[2])&&(inter_color[0]!=fillcolor[0]&&inter_color[1]!=fillcolor[1]&&inter_color[2]!=fillcolor[2]))
{
setpixel(x,y,fillcolor);
bfill(x+1,y,fillcolor,bordercolor);
bfill(x-1,y,fillcolor,bordercolor);
bfill(x,y+1,fillcolor,bordercolor);
bfill(x,y-1,fillcolor,bordercolor);
}
}
 void mouse(int btn,int state,int x,int y) 
  { 
     if(btn==GLUT_LEFT_BUTTON && state==GLUT_DOWN) 
     { 
              xi=x; 
               yi=wh-y;
printf("\nPoints collected are:%d and %d",xi,yi);
bfill(xi,yi,fillcol,bordercol);   
     }
  }

 int main(int argc,char** argv) 
 {
glutInit(&argc,argv); 
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); 
glutInitWindowSize(ww,wh);
glutInitWindowPosition(0,0);
glutCreateWindow("CheckBox(Click on any box to fill color)"); 
glutDisplayFunc(display); 
glutMouseFunc(mouse); 
glutMainLoop(); 
return 0;
  }