10. Graphics Program to draw a line using Bresenham’s Line drawing

#include <GL/gl.h>

#include <GL/glut.h>

#include <stdio.h>

int x1,y1,x2,y2;

void myInit()

{

glClear(GL_COLOR_BUFFER_BIT);

glClearColor(0.0,0.0,0.0,1.0);

glMatrixMode(GL_PROJECTION);

gluOrtho2D(0,500,0,500);

}

void draw_pixel(int x,int y)

{

glBegin(GL_POINTS);

glVertex2f(x,y);

glEnd();

}

void draw_line(int x1,int x2,int y1,int y2)

{

int dx,dy,i,e;

int incx,incy,inc1,inc2;

int x,y;

dx=x2-x1;

dy=y2-y1;

if(dx<0) dx=-dx;

if(dx<0) dy=-dy;

incx=1;

if(x2<x1) incx=1;

incy=1;

if(y2<y1) incy=1;

x=x1;

y=y1;

if(dx>dy)

{

draw_pixel(x,y);

e=2*(dy-dx);

inc1=2*dy-dx;

inc2=2*dy;

for(i=0; i<dx; i++)

{

if(e>=0)

{

y+=incy;

e+=inc1;

}

else

e+=inc2;

x+=incx;

draw_pixel(x,y);

}

}

else

{

draw_pixel(x,y);

e=2*dx-dy;

inc1=2*(dx-dy);

inc2=2*dx;

for(i=0; i<dy; i++)

{

if(e>=0)

{

x+=incx;

e+=inc1;

}

else

e+=inc2;

y+=incy;

draw_pixel(x,y);

}

    }

    }

    void myDisplay()

    {

     draw_line(x1,x2,y1,y2);

     glFlush();

    }

    int main(int argc, char** argv)

    {

     printf("Enter (x1,y1,x2,y2)\n");

     scanf("%d %d %d %d", &x1, &y1, &x2, &y2);

     glutInit(&argc, argv);

     glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);

     glutInitWindowSize(500,500);

     glutInitWindowPosition(0,0);

     glutCreateWindow("Bresenham's Line Drawing");

     myInit();

     glutDisplayFunc(myDisplay);

     glutMainLoop();

     return(0);

    }