Computer-Graphics/ScanLine.cpp at main · AmithChatriki/Computer-Graphics · GitHub

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#include <stdlib.h>
#include <stdio.h>
#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, x, 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;
	x = x1;
	for (i = y1;i <= y2;i++)
	{
		if (x < (float)le[i])
			le[i] = (int)x;
		if (x > (float)re[i])
			re[i] = (int)x;
		x += mx;
	}
}
void draw_pixel(int x, int y)
{
	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, y;
	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 (y = 0;y < 500;y++)
	{
		for (i = (int)le[y];i < (int)re[y];i++)
			draw_pixel(i, y);
	}
}
void display()
{
	x1 = 200.0;y1 = 200.0;x2 = 100.0;y2 = 300.0;x3 = 200.0;y3 = 400.0;x4 = 300.0;y4 = 300.0;
	glClear(GL_COLOR_BUFFER_BIT);

	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(0.0, 0.0, 0.0, 1.0);
	glColor3f(1.0, 0.0, 0.0);
	glPointSize(1.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0.0, 499.0, 0.0, 499.0);
}
void fillMenu(int option)
{
	if (option == 1) {
		fillFlag = 1;
		glColor3f(0.0, 1.0, 0.0);
	}
	if (option == 2) {
		fillFlag = 1;
		glColor3f(1.0, 0.0, 0.0);
	}
	if (option == 3) {
		fillFlag = 2;
	}
	glutPostRedisplay();
	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");
	init();
	glutDisplayFunc(display);
	glutCreateMenu(fillMenu);
	glutAddMenuEntry("Fill Green", 1);
	glutAddMenuEntry("Fill Red", 2);
	glutAddMenuEntry("Empty Polygon", 3);
	glutAttachMenu(GLUT_RIGHT_BUTTON);
	glutMainLoop();
}