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#include 
   
    #include
    
     #pragma comment(linker, "/subsystem:\"windows\" /entry:\"mainCRTStartup\"")int SCREEN_HEIGHT = 600;int NUMPOINTS = 0;class Point{   	public:	float x, y;	void setxy(float x2, float y2)	{   		x = x2;		y = y2;	}};Point abc[4];Point bef[3];Point mid[2];Point link[1000];void myInit(){   	glClearColor(0.0, 0.0, 0.0, 0.0);	glColor3f(1.0f, 0.0, 0.0);	glPointSize(4.0);	glMatrixMode(GL_PROJECTION);	glLoadIdentity();	gluOrtho2D(0.0, 640, 0.0, 480.0);}void drawDot(Point pt){   	glBegin(GL_POINTS);	glVertex2f(pt.x, pt.y);	glEnd();	glFlush();	}	void drawLine(Point p1, Point p2)	{   	glBegin(GL_LINES);	glVertex2f(p1.x, p1.y);	glVertex2f(p2.x, p2.y);	glEnd();	glFlush();}//四个控制点的贝塞尔曲线 即三次Bezier曲线  void drawBezier(Point A, Point B, Point C, Point D){   	for (double t = 0.0; t <= 1.0; t += 0.001)	{   		bef[0].setxy((1 - t)*A.x + t*B.x, (1 - t)*A.y + t*B.y);		bef[1].setxy((1 - t)*B.x + t*C.x, (1 - t)*B.y + t*C.y);		bef[2].setxy((1 - t)*C.x + t*D.x, (1 - t)*C.y + t*D.y);						mid[0].setxy((1 - t)*bef[0].x + t*bef[1].x, (1 - t)*bef[0].y + t*bef[1].y);		mid[1].setxy((1 - t)*bef[1].x + t*bef[2].x, (1 - t)*bef[1].y + t*bef[2].y);						link[0].setxy((1 - t)*mid[0].x + t*mid[1].x, (1 - t)*mid[0].y + t*mid[1].y);				glColor3f(1.0f, 1.0f, 0.0f);		drawLine(bef[0], bef[1]);		glColor3f(1.0f, 1.0f, 0.0f);		drawLine(bef[1], bef[2]);		glColor3f(1.0f, 1.0f, 0.0f);		drawLine(mid[0], mid[1]);				glColor3f(1.0f, 0.0f, 0.0f);		drawDot(link[0]);				glColor3f(0.0f, 0.0f, 0.0f);		drawLine(bef[0], bef[1]);		glColor3f(0.0f, 0.0f, 0.0f);		drawLine(bef[1], bef[2]);		glColor3f(0.0f, 0.0f, 0.0f);		drawLine(mid[0], mid[1]);					glColor3f(0.0, 1.0, 0.0);	drawLine(abc[0], abc[1]);	glColor3f(0.0, 1.0, 0.0);	drawLine(abc[1], abc[2]);	glColor3f(0.0, 1.0, 0.0);	drawLine(abc[2], abc[3]);	}}void myDisplay(){   	glClear(GL_COLOR_BUFFER_BIT);	glFlush();}void ChangeSize(GLsizei width, GLsizei height){   	GLfloat aspect_init, aspect;	glViewport(0, 0, width, height);	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	aspect_init = 4.0 / 3.0;	aspect = 1.0*width / height;	glMatrixMode(GL_PROJECTION);	glLoadIdentity();	//Keep Aspect of Current Window	if (aspect <= aspect_init)	glViewport(0, (height - width / aspect) / 2, width, width / aspect_init);	else	glViewport((width - height*aspect_init) / 2, 0, height*aspect_init, height);	glMatrixMode(GL_MODELVIEW);	glLoadIdentity();	glOrtho(-2, 2, -2, 2, -2, 2);}void myMouse(int button, int state, int x, int y){   if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN){   	abc[NUMPOINTS].setxy((float)x, (float)(SCREEN_HEIGHT - y));	NUMPOINTS++;	if (NUMPOINTS == 4)	{   		glColor3f(1.0, 0.0, 1.0);		drawDot(abc[0]);		glColor3f(1.0, 0.0, 1.0);		drawDot(abc[1]);		glColor3f(1.0, 0.0, 1.0);		drawDot(abc[2]);		glColor3f(1.0, 0.0, 1.0);		drawDot(abc[3]);		glColor3f(0.0, 1.0, 0.0);		drawLine(abc[0], abc[1]);		glColor3f(0.0, 1.0, 0.0);		drawLine(abc[1], abc[2]);		glColor3f(0.0, 1.0, 0.0);		drawLine(abc[2], abc[3]);		//Point POld = abc[0];				drawBezier(abc[0], abc[1], abc[2], abc[3]);		glColor3f(1.0, 0.0, 1.0);		drawDot(abc[0]);		glColor3f(0.0, 1.0, 0.0);		drawLine(abc[0], abc[1]);		glColor3f(0.0, 1.0, 0.0);		drawLine(abc[1], abc[2]);		glColor3f(0.0, 1.0, 0.0);		drawLine(abc[2], abc[3]);		glColor3f(1.0, 0.0, 0.0);		NUMPOINTS = 0;	}	}}void main(int argc, char **argv){   	glutInit(&argc, argv);		// 在这里设置双缓冲区。        	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);	glutInitWindowPosition(0, 0);	glutInitWindowSize(800, 600);	glutCreateWindow("bezier");	glutMouseFunc(myMouse);		myInit();	//glutIdleFunc(RenderScene);	glutDisplayFunc(myDisplay);	glutMainLoop();}