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prog7.c
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prog7.c
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/*
Write a program to fill any given 2D polygon using scan-line area filling algorithm.
*/
#include<stdio.h>
#include<GL/glut.h>
#define WIDTH 500
#define HEIGHT 500
struct point {
int x,y;
};
struct point points[10];
int nPoints;
int LE[500], RE[500];
void drawPixel(int x, int y)
{
glBegin(GL_POINTS);
glVertex2f(x,y);
glEnd();
}
void edgeDetect(int x1, int y1, int x2, int y2)
{
if(y2<y1)
{
int temp = x1;
x1 = x2;
x2 = temp;
temp = y1;
y1 = y2;
y2 = temp;
}
float m;
if(y2-y1 == 0)
m = x2-x1;
else
m = (x2-x1)/(y2-y1);
int x = x1;
for(int y=y1; y<=y2; y++)
{
if(x<LE[y])
LE[y] = x;
if(x>RE[y])
RE[y] = x;
x += m;
}
}
void display()
{
// draw polygon
glColor3f(1,0,0);
glBegin(GL_LINE_LOOP);
for(int i=0; i<nPoints; i++)
glVertex2f(points[i].x, points[i].y);
glEnd();
// scan line filling
glColor3f(0,1,0);
for(int i=0; i<500; i++)
{
LE[i] = 500;
RE[i] = 0;
}
for(int i=0; i<nPoints; i++)
edgeDetect(points[i].x, points[i].y, points[(i+1)%nPoints].x, points[(i+1)%nPoints].y);
for(int y=0; y<500; y++)
if(LE[y] <= RE[y])
for(int x=LE[y]; x<=RE[y]; x++)
{
drawPixel(x,y);
glFlush();
}
glFlush();
}
void myInit()
{
// set background
glClearColor(1,1,1,1);
glClear(GL_COLOR_BUFFER_BIT);
// set camera
gluOrtho2D(0,WIDTH,0,HEIGHT);
}
int main(int argc, char *argv[])
{
// printf("\nEnter number of points - ");
// scanf("%d", &nPoints);
// printf("\nEnter all points -\n");
// for(int i=0; i<nPoints; i++)
// scanf("%d%d", &points[i].x, &points[i].y);
nPoints = 4;
points[0].x = 100; points[0].y = 250;
points[1].x = 250; points[1].y = 100;
points[2].x = 400; points[2].y = 250;
points[3].x = 250; points[3].y = 400;
glutInit(&argc, argv);
glutInitWindowSize(WIDTH, HEIGHT);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutCreateWindow("Scan line polygon fill");
myInit();
glutDisplayFunc(display);
glutMainLoop();
return 0;
}