3.cpp

/*实验 梁友栋窗口切割*/

#include"pch.h"
#include"GL/glut.h"
#include<cstdio>

static GLsizei iMode = 1;
int iPointNum = 0;
int x1 = 0, x2 = 0, y1 = 0, y2 = 0;
int winWidth = 400, winHeight = 300;
int addw = 200, addh = 150;
void Initial(void) {
	glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
}
void ChangeSize(int w, int h) {
	winWidth = w; winHeight = h;
	addw = winWidth >> 1; addh = winHeight >> 1;
	glViewport(0, 0, w, h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0.0, winWidth, 0.0, winHeight);
}
inline void putpixel(int x, int y) {
	glBegin(GL_POINTS);
	glVertex2d(x + addw, y + addh);
	glEnd();
}
void MidBresenhamline(int x0, int y0, int x1, int y1) {
	int dx, dy, d, UpIncre, DownIncre, x, y;
	if (x0 > x1) {
		x = x1; x1 = x0; x0 = x;
		y = y1; y1 = y0; y0 = y;
	}
	x = x0; y = y0;
	dx = x1 - x0;	dy = y1 - y0; d = dx - 2 * dy;
	UpIncre = 2 * dx - 2 * dy; DownIncre = -2 * dy;
	while (x <= x1) {
		x++;
		if (d < 0)y++, d += UpIncre;
		else d += DownIncre;
	}
}
int LBLineClipTest(float p, float q, float &umax, float &umin) {
	float r = 0.0;
	if (p < 0.0) {
		r = q / p;
		if (r > umin) return 0;
		else if (r > umax) umax = r;
	}
	else if (q < 0.0) return 0;
	return 1;
}
void LBLineClip(int xwl, int xwr, int ywb, int ywt, int x1, int y1, int x2, int y2) {
	float umax, umin, deltax, deltay;
	deltax = x2 - x1; deltay = y2 - y1; umax = 0.0; umin = 1.0;
	if (LBLineClipTest(-deltax, x1 - xwl, umax, umin)) {
		if (LBLineClipTest(deltax, xwr - x1, umax, umin)) {
			if (LBLineClipTest(-deltay, y1 - ywb, umax, umin)) {
				if (LBLineClipTest(deltay, ywt - y1, umax, umin)) {
					x1 = int(x1 + umax * deltax + 0.5);
					y1 = int(y1 + umax * deltay + 0.5);
					x1 = int(x2 + umin * deltax + 0.5);
					y1 = int(y2 + umin * deltay + 0.5);
				}
				glBegin(GL_LINES);
				glColor3f(0.0, 1.0, 0.0);
				glVertex2f(x1, y1);
				glVertex2f(x2, y2);
				glEnd();
				glFlush();
				//MidBresenhamline((int)x1, (int)y1, (int)x2, (int)y2);
				//printf("%d %d %d %d\n",x1,y1,x2,y2);
				//system("pause");
			}
		}
	}
	int a[] = { xwl,xwl,xwr,xwr,xwl };
	int b[] = { ywb,ywt,ywt,ywb,ywb };
	for (int i = 0; i < 4; i++) {
		glBegin(GL_LINES);
		glVertex2i(a[i], b[i]);
		glVertex2i(a[i + 1], b[i + 1]);
		glEnd();
	}

}
void Display(void) {
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(1.0f, 0.0f, 0.0f);
	if (iPointNum >= 1) {
		//x1 += addw; x2 += addw;
		//y1 += addh; y2 += addh;
		switch (iMode)
		{
		case 1:
			LBLineClip(0, addh, winWidth, addh,x1, x2, y1, y2);
			break;
		case 2:
			LBLineClip(x1, x2, y1, y2, addw, 0, addw, winHeight);
			break;
		case 3:
			LBLineClip(x1, x2, y1, y2, 0, 0, winWidth, winHeight);
			break;
		default:
			break;
		}

	}
	if (iPointNum < 2) {
		switch (iMode) {
		case 1:
			glBegin(GL_LINES);
			glVertex2i(0, addh);
			glVertex2i(winWidth, addh);
			glEnd();
			break;
		case 2:
			glBegin(GL_LINES);
			glVertex2i(addw, 0);
			glVertex2i(addw, winHeight);
			glEnd();
			break;
		case 3:
			glBegin(GL_LINES);
			glVertex2i(0, 0);
			glVertex2i(winWidth, winHeight);
			glEnd();
			break;
		default:
			break;
		}
	}
	glutSwapBuffers();
}

void MousePlot(GLint button, GLint action, GLint xMouse, GLint yMouse) {
	if (button == GLUT_LEFT_BUTTON && action == GLUT_DOWN) {
		//puts("leftkey click");
		//printf("ipoint=%d\n",iPointNum);
		if (iPointNum == 0 || iPointNum == 2) {
			iPointNum = 1;
			x1 = xMouse; y1 = winHeight - yMouse;

		}
		else {
			x2 = xMouse; y2 = winHeight - yMouse;
			iPointNum = 2;
			glutPostRedisplay();
		}
	}
	if (button == GLUT_RIGHT_BUTTON && action == GLUT_DOWN) {
		iPointNum = 0;
		glutPostRedisplay();
	}
	//printf("ipoint=%d x=%d y=%d\n",iPointNum,x1,y1);
}

void Key(unsigned char key, int x, int y) {
	switch (key)
	{
	case 'p':
		if (iPointNum == 0 || iPointNum == 2) {
			iPointNum = 1;
			x1 = x; y1 = winHeight - y;
		}
		else {
			x2 = x; y2 = winHeight - y;

			iPointNum = 2;
			glutPostRedisplay();

		}
		break;
	case 'c':
		iPointNum = 0;
		glutPostRedisplay();
		break;
	default:
		break;
	}
}

void PassiveMouseMove(GLint xMouse, GLint yMouse) {
	if (iPointNum == 1) {
		x2 = xMouse; y2 = winHeight - yMouse;
		glutPostRedisplay();

	}

}
void ProcessMenu(int value) {
	iMode = value;
	glutPostRedisplay();
}
int main(int argc, char* argv[]) {
	glutInit(&argc, argv);		//对GLUT库进行初始化
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);	//设定窗口的显示模式，包括缓存和颜色模型等
	glutInitWindowSize(400, 300);		//设置窗口大小400x300
	glutInitWindowPosition(100, 120);	//设置窗口位置（Windows下右上角为(0,0)）
	glutCreateWindow("椭圆的中点Bresenham算法");			//创建一个名为矩形的窗口
	int nGlutLineMenu = glutCreateMenu(ProcessMenu);
	glutAddMenuEntry("- line", 1);
	glutAddMenuEntry("| line", 2);
	glutAddMenuEntry("/ line", 3);
	glutAttachMenu(GLUT_RIGHT_BUTTON);
	glutDisplayFunc(Display);			//设置当前窗口的回调函数（即窗口显示的内容）
	glutReshapeFunc(ChangeSize);
	glutMouseFunc(MousePlot);	//鼠标响应
	glutKeyboardFunc(Key);
	glutPassiveMotionFunc(PassiveMouseMove);
	Initial();					//完成窗口初始化
	glutMainLoop();			//启动主GLUT事件处理循环
	return 0;
}