//#pragma comment( linker, "/subsystem:windows /entry:mainCRTStartup" )//去除控制台窗口 #include #include #include #include #include #include #include using namespace std; struct Point { float x, y; Point(float _x, float _y) :x(_x), y(_y) {} Point() {} void operator =(Point& r) { x = r.x; y = r.y; } }; Point vertex[2]; int down_cnt = 1; //记录点击的次数 int choice_id = -1; int window_size = 800; float XL=200, XR=600, YB=200, YT=600; void draw_rectangle(); void grey_line(float x1,float y1,float x2,float y2); void green_line(float x1, float y1, float x2, float y2); void draw_rp(float x, float y); void OnMouse(int button, int state, int x, int y); void InitEnvironment(); bool ClipT(float p, float q, float* u1, float* u2); void LB_LineClip(float x1, float y1, float x2, float y2); void myMotion(int x, int y); int main(int argc, char* argv[]) { glutInit(&argc, argv); //初始化GLUT glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE); glutInitWindowPosition(300, 100); glutInitWindowSize(window_size, window_size); glutCreateWindow("liang_Barskey"); InitEnvironment(); //初始化 glutMotionFunc(&myMotion); //回调函数 glutMouseFunc(&OnMouse); //注册鼠标事件 glutMainLoop(); //持续显示，当窗口改变会重新绘制图形 return 0; } void InitEnvironment() { glClearColor(0.0, 0.0, 0.0, 1); glClear(GL_COLOR_BUFFER_BIT); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glPointSize(6); glLineWidth(3); gluOrtho2D(0, window_size, 0, window_size); draw_rectangle(); } void myMotion(int x, int y) { if (choice_id != -1) { vertex[choice_id].x = float(x); vertex[choice_id].y = float(y); LB_LineClip(vertex[0].x, vertex[0].y, vertex[1].x, vertex[1].y); } } void draw_rectangle() { glBegin(GL_LINES); glColor3f(1, 1, 0); glVertex2f(XL, window_size - YB); glVertex2f(XR, window_size - YB); glVertex2f(XL, window_size - YT); glVertex2f(XR, window_size - YT); glVertex2f(XL, window_size - YB); glVertex2f(XL, window_size - YT); glVertex2f(XR, window_size - YB); glVertex2f(XR, window_size - YT); glEnd(); glFlush(); } void draw_rp(float x, float y) { glBegin(GL_POINTS); glColor3f(1, 0, 0); glVertex2f(x, window_size - y); glEnd(); glFlush(); } void OnMouse(int button, int state, int x, int y) //OnMouse坐标系x从左向右，y从上到下 { if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) { if (down_cnt ==1) { vertex[0].x = float(x); vertex[0].y = float(y); draw_rp(x, y); } else if(down_cnt ==2){ vertex[1].x = float(x); vertex[1].y = float(y); draw_rp(x, y); LB_LineClip(vertex[0].x, vertex[0].y, vertex[1].x, vertex[1].y); } else { choice_id = -1; for (int i = 0; i < 2; i++) { if (abs(x - vertex[i].x) < 8 && abs(y - vertex[i].y) < 8) {//选中一个点 choice_id = i; break; } } } down_cnt++; } else if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN ) { //点击右键，选择顶点拖动 } } void grey_line(float x1, float y1, float x2, float y2) { glBegin(GL_LINES); glColor3f(0.5, 0.5, 0.5); glVertex2f(x1, window_size - y1); glVertex2f(x2, window_size - y2); glEnd(); glFlush(); } void green_line(float x1, float y1, float x2, float y2) { glBegin(GL_LINES); glColor3f(0, 1, 0); glVertex2f(x1, window_size - y1); glVertex2f(x2, window_size - y2); glEnd(); glFlush(); } bool ClipT(float p, float q, float* u1, float* u2) { float r; if (p < 0) { r = q / p; if (r > * u2)return FALSE; if (r > * u1)* u1 = r; } else if (p > 0) { r = q / p; if (r < *u1)return FALSE; if (r < *u2)* u2 = r; } else return (q >= 0); return TRUE; } void LB_LineClip(float x1, float y1, float x2, float y2) { float dx, dy, u1, u2; u1 = 0, u2 = 1; dx = x2 - x1; dy = y2 - y1; glClear(GL_COLOR_BUFFER_BIT); draw_rectangle(); draw_rp(x1, y1); draw_rp(x2, y2); grey_line(x1, y1, x2, y2); if(ClipT(-dx,x1-XL,&u1,&u2)) if(ClipT(dx,XR-x1,&u1,&u2)) if(ClipT(-dy,y1-YB,&u1,&u2)) if (ClipT(dy, YT - y1, &u1, &u2)) { green_line(x1 + u1 * dx, y1 + u1 * dy, x1 + u2 * dx, y1 + u2 * dy); } }
