bresenham_circle.cpp

#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

#include <bits/stdc++.h>
using namespace std;


void initialize()
{
    glClearColor(0.0, 0.0, 0.0, 1.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D (0.0, 640.0, 0.0, 480.0);
}

void BCDA()
{
    double xCenter = 300 ;
    double yCenter = 200;
    double radius = 100;

    double x = 0;
    double y = radius;
    double d = 3 - 2*radius;//5/4 is rounded to 1 for integer radius

    glBegin(GL_POINTS);
        glColor3f(1.0, 0.0, 0.0);
        glVertex2i(xCenter,yCenter);
    glEnd();

    glColor3f(0.0, 1.0, 0.0);

    while(x <= y)   // iterates to draw the first sector
    {
        x++;
        if(d < 0){// the mid point is inside the circle
            d = d + 4*x + 6;
        }
        else  // the mid point is outside or at the circle
        {
            y--;
            d = d + 4*(x - y) + 10;
        }
        glBegin(GL_POINTS);
            glVertex2i(xCenter + x, yCenter + y);
            glVertex2i(xCenter - x, yCenter + y);
            glVertex2i(xCenter + x, yCenter - y);
            glVertex2i(xCenter - x, yCenter - y);
            glVertex2i(xCenter + y, yCenter + x);
            glVertex2i(xCenter - y, yCenter + x);
            glVertex2i(xCenter + y, yCenter - x);
            glVertex2i(xCenter - y, yCenter - x);
        glEnd();
    }
}

void draw()
{

    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0, 10.0, 20.0);
    double sz = 2;
    //cin >> sz;
    glPointSize(sz);
    BCDA();
    glFlush(); // send all output to the display
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitWindowSize(2000, 2000); // set the size of the window
    glutInitWindowPosition(0, 0); // the position of the top-left of window
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);

    glutCreateWindow("Bresenham ’s Line Drawing Algorithm");

    initialize();

    glutDisplayFunc(draw); // set the gl display callback function
    glutMainLoop(); // enter the GL event loop

}