Filling.txt

#include<GL/glut.h>

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

void draw_pixel(int x, int y)
{
	glColor3f(0.0, 1.0, 0.0);
	glPointSize(1.0);
	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;
	glClear(GL_COLOR_BUFFER_BIT);
	glBegin(GL_LINE_LOOP);
	glVertex2f(100, 300);
	glVertex2f(200, 100);
	glVertex2f(200, 200);
	glVertex2f(100, 200);
	glEnd();

	scanfill(100, 300, 200, 100, 200, 200, 100, 200);

	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();
}