用OpenGL实现 中点划线法

#include "GL/glut.h"
#include "stdio.h"
#include "math.h"

int xs, ys, xe, ye;

void MidpointLine(int x0, int y0, int x1, int y1)
{
	if((x0 != x1) && (y0 != y1))
	{
		int a, b, deltal, delta2, d, x, y;
		a = y0 - y1;
		b = x1 - x0;
		d = 2 * a + b;
		deltal = 2 * a;
		delta2 = 2 * (a + b);
		x = x0;
		y = y0;
		glVertex2i(x, y);
		while(x < x1)
		{
			if(d < 0)
			{
				x++;
				y++;
				d += delta2;
			}
			else
			{
				x++;
				d += deltal;
			}
			glVertex2i(x, y);
		}
	}
	else
	{
		int min, d;
		if(x0 == x1)
		{
			int x = x0, y;
			y = (y0<=y1) ? y0 : y1;
			d = fabs((double)(y0 - y1));
			while (d <= 0)
			{
				glVertex2i(x, y);
				y++;
				d--;
			}
		}
	}
}

void lineSegment()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(0.0, 0.0, 0.0);
	glBegin(GL_POINTS);
	MidpointLine(xs, ys, xe, ye);
	glEnd();
	glFlush();
}

void main(int argc, char * argv[])
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
	printf("输入线段起始和终止点坐标（范围为0-500,0-500）");
	scanf("%d, %d, %d, %d", &xs, &ys, &xe, &ye);
	glutInitWindowPosition(50, 100);
	glutInitWindowSize(500, 500);
	glutCreateWindow("中点划线法");
	glClearColor(1.0, 1.0, 1.0, 0.0);
	glMatrixMode(GL_PROJECTION);
	gluOrtho2D(0.0, 500.0, 0.0, 500.0);
	glutDisplayFunc(lineSegment);
	glutMainLoop();
}