cg/9cg.c at master · mohammedlutf/cg · GitHub

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#include <GL/glut.h>


float x1,x2,x3,x4,y1,y2,y3,y4;
int fillFlag=0;

void edgedetect(float x1,float y1,float x2,float y2,int *le,int *re)
{
	float mx,temp;
	int i;

	if((y2-y1)<0)
	{

		temp=y1;y1=y2;y2=temp;
		temp=x1;x1=x2;x2=temp;
	}
	if((y2-y1)!=0)
	mx=(x2-x1)/(y2-y1);

	else
	mx=x2-x1;

	for(i=y1;i<=y2;i++)
	{

		if(x1<le[i])
		   le[i]=x1;
		if(x1>re[i])
		   re[i]=x1;
		x1+=mx;

	}
}


void draw_pixel(int x,int y)
{
	glColor3f(1.0,1.0,0.0);
   glBegin(GL_POINTS);
	  glVertex2i(x,y);
	glEnd();
}

void scanfill(float x1,float y1,float x2,float y2,float x3,float y3,float x4,float y4)

{
	int le[500],re[500];
	int i,j;

	for(i=0;i<500;i++)
	{

		le[i]=500;
		re[i]=0;
	}
	edgedetect(x1,y1,x2,y2,le,re);
	edgedetect(x2,y2,x3,y3,le,re);
	edgedetect(x3,y3,x4,y4,le,re);
	edgedetect(x4,y4,x1,y1,le,re);

	for(j=0;j<500;j++)
	  for(i=le[j];i<re[j];i++)
		    draw_pixel(i,j);

}


void display()
{

	x1=200.0;y1=200.0;x2=200.0;y2=300.0;x3=300.0;y3=300.0;x4=300.0;y4=200.0;
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(0.0, 0.0, 1.0);
	glBegin(GL_LINE_LOOP);
	glVertex2f(x1,y1);
	glVertex2f(x2,y2);
	glVertex2f(x3,y3);
	glVertex2f(x4,y4);
	glEnd();
	if(fillFlag==1)
	scanfill(x1,y1,x2,y2,x3,y3,x4,y4);
	glFlush();
}

void init()
{
	glClearColor(1.0,1.1,1.0,1.0);

	gluOrtho2D(0.0,499.0,0.0,499.0);
}

void fillMenu(int option)
{
	if(option==1)
	   fillFlag=1;
	if(option==2)
	   fillFlag=2;
	display();
}

void main(int argc, char* argv[])
{
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
	glutInitWindowSize(500,500);
	glutInitWindowPosition(0,0);
	glutCreateWindow("Filling a Polygon using Scan-line Algorithm");
	glutDisplayFunc(display);
	glutCreateMenu(fillMenu);
	glutAddMenuEntry("Fill Polygon",1);
	glutAddMenuEntry("Empty Polygon",2);
	glutAttachMenu(GLUT_RIGHT_BUTTON);
	init();
    glutMainLoop();
}