Bresenham_Line_Drawing_Algorithm.c

// This is Algorithm for Bresenham Line Drawing.

# include<GL/glut.h>
# include <stdio.h>
int x1, y1, x2, y2;
void myInit()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glClearColor(0.0, 0.0, 0.0, 1.0);
	glMatrixMode(GL_PROJECTION);
	gluOrtho2D(0, 500, 0, 500);
}
void draw_pixel(int x, int y)
{
	glBegin(GL_POINTS);
	glVertex2i(x, y);
	glEnd();
}
void draw_line(int x1, int x2, int y1, int y2)
{
	int dx, dy, i, e;
	int incx, incy, inc1, inc2;
	int x, y;
	dx = x2 - x1;
	dy = y2 - y1;
	if (dx < 0) dx = -dx;
	if (dy < 0) dy = -dy;
	incx = 1;
	if (x2 < x1)
		incx = -1;
	incy = 1;
	if (y2 < y1) incy = -1;
	x = x1; y = y1;
	if (dx > dy)
	{
		draw_pixel(x, y);
		e = 2 * dy - dx;
		inc1 = 2 * (dy - dx);
		inc2 = 2 * dy;
		for (i = 0; i < dx; i++) {
			if (e >= 0) {
				y += incy;
				e += inc1;
			}
			else
				e += inc2;
			x += incx;
			draw_pixel(x, y);
		}
	}
	else {
		draw_pixel(x, y);
		e = 2 * dx - dy;
		inc1 = 2 * (dx - dy);
		inc2 = 2 * dx;
		for (i = 0; i < dy; i++)
		{
			if (e >= 0)
			{
				x += incx;
				e += inc1;
			}
			else
				e += inc2;
			y += incy;
			draw_pixel(x, y);
		}
	}
}
void myDisplay() {
	draw_line(x1, x2, y1, y2);
	glFlush();
}
void main(int argc, char** argv) {
	printf("Enter (x1, y1, x2, y2)\n");
	scanf_s("%d %d %d %d", &x1, &y1, &x2, &y2);
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutInitWindowSize(500, 500);
	glutInitWindowPosition(0, 0);
	glutCreateWindow("Bresenham's Line Drawing");
	myInit();
	glutDisplayFunc(myDisplay); glutMainLoop();
}