Write a program in c to implement scan-line polygon filling algorithm?

Answer 1

#include<GL/glut.h>

float x1,x2,x3,x4,y1,y2,y3,y4;

void draw_pixel(int x,int y)

{

glColor3f(0.5,0.0,1.0);

glPointSize(0.5);

glBegin(GL_POINTS);

glVertex2i(x,y);

glEnd();

}

void edgedetect(float x1,float y1,float x2,float y2,int *le,int *re)

{

float temp,x,mx;

int i;

if(y1>y2)

{

temp=x1,x1=x2,x2=temp;

temp=y1,y1=y2,y2=temp;

}

if(y1==y2)

mx=x2-x1;

else

mx=(x2-x1)/(y2-y1);

x=x1;

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

{

if(x<(float)le[i]) le[i]=(int)x;

if(x>(float)re[i]) re[i]=(int)x;

x+=mx;

}

}

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

{

int le[500],re[500],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++)

{

if(le[j]<=re[j])

for(i=le[j];i<re[j];i++)

draw_pixel(i,j);

}

}

void display()

{

x1=250.0;y1=200.0;x2=150.0;y2=300.0;x3=250.0;

y3=400.0;x4=350.0;y4=300.0;

glBegin(GL_TRIANGLES);

glVertex2f(x1,y1);

glVertex2f(x2,y2);

glVertex2f(x3,y3);

glVertex2f(x4,y4);

glEnd();

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

glFlush();

}

void init()

{

glClearColor(1.0,1.0,1.0,1.0);

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

gluOrtho2D(0.0,499.0,0.0,499.0);

}

void main(int argc,char **argv)

{

glutInit(&argc,argv);

glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);

glutInitWindowSize(500,500);

glutCreateWindow("scanline");

glutDisplayFunc(display);

init();

glutMainLoop();

}