计算机图形学实验-基于OpenGL实现椭圆 Bresenham 算法和橡皮筋交互技术

#include "onMidPointEllispe.h" /************************************************** * 已知椭圆的长短轴a,b * 根据椭圆的中点Bresenham算法，扫描转换椭圆 * 以glBegin(GL_POINTS);glEnd();方式，绘制椭圆 ***************************************************/ void onMidPointEllispe(int a,int b){ int x,y; float d1,d2; glBegin(GL_POINTS); x=0;y=b; d1=b*b+a*a*(-b+0.25); glVertex2i(x,y); glVertex2i(-x,-y); glVertex2i(-x,y); glVertex2i(x,-y); while(b*b*(x+1)<a*a*(y-0.5)) { if(d1<=0){ d1+=b*b*(2*x+3); x++; } else{ d1+=b*b*(2*x+3)+a*a*(-2*y+2); x++; y--; } glVertex2f(x,y); glVertex2f(-x,-y); glVertex2f(-x,y); glVertex2f(x,-y); }/*while上半部分*/ d2=b*b*(x+0.5)*(x+0.5)+a*a*(y-1)*(y-1)-a*a*b*b; while(y>0) { if(d2<=0){ d2+=b*b*(2*x+2)+a*a*(-2*y+3); x++; y--; } else{ d2+=a*a*(-2*y+3); y--; } glVertex2f(x,y); glVertex2f(-x,-y); glVertex2f(-x,y); glVertex2f(x,-y); } glEnd(); } void drawRect(vector<Point> p){ int x1,y1,x2,y2; x1 = p[0].x; y1 = p[0].y; x2 = p[1].x; y2 = p[1].y; if(iPointNum == 1){ glColor3f(1.0f, 0.0f, 0.0f); glBegin(GL_LINE_STRIP); glVertex2i(x1,y1); glVertex2i(x1,y2); glVertex2i(x2,y2); glVertex2i(x2,y1); glVertex2i(x1,y1); glEnd(); point center; center.x = (x1 + x2)/2; center.y = (y1 + y2)/2; glTranslated(center.x, center.y, 0.0); int a = abs(x1-x2)/2; int b = abs(y1-y2)/2; glColor3f(0.0f, 0.0f, 1.0f); onMidPointEllispe(a, b); glTranslated(-center.x, -center.y, 0.0); } if(iPointNum == 0 || iPointNum == 2){ point center; center.x = (x1 + x2)/2; center.y = (y1 + y2)/2; glTranslated(center.x, center.y, 0.0); int a = abs(x1-x2)/2; int b = abs(y1-y2)/2; glColor3f(0.0f, 0.0f, 1.0f); onMidPointEllispe(a, b); glTranslated(-center.x, -center.y, 0.0); p.clear(); x1 = 0, y1 = 0, x2 = 0 , y2 = 0; iPointNum = 0; } p.clear(); } void init(){ glClearColor(1.0f, 1.0f, 1.0f, 1.0f); //设置背景颜色为白色 } void ChangeSize(int w,int h) { winWidth=w; winHeight=h; glViewport(0,0,w,h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); //调用单位矩阵，去除以前投影参数设置 gluOrtho2D(0.0,winWidth,0.0,winHeight); } void Display(){ glClear(GL_COLOR_BUFFER_BIT); //用背景色填充窗口 glColor3f(0.0f, 0.0f, 1.0f); //指定绘图颜色 drawRect(p); // glFlush(); glutSwapBuffers(); //交换缓冲区 } void ProcessMenu(int value){ if(value == 1){ cout << "菜单选择“椭圆”，可以绘制\n" << endl; draw = true; } else{ cout << "菜单选择“退出”，不可绘制\n" << endl; draw = false; square = false; glClear(GL_COLOR_BUFFER_BIT); glutSwapBuffers(); } } void createMenus(){ glutCreateMenu(ProcessMenu); //创建菜单，ProcessMenu处理菜单事件 glutAddMenuEntry("Ellispe", 1); //给菜单增加“椭圆”条目 glutAddMenuEntry("exit", 0); //给菜单增加“退出”条目 glutAttachMenu(GLUT_RIGHT_BUTTON); //把菜单和鼠标右键关联 } void MousePlot(GLint button,GLint action,GLint xMouse,GLint yMouse) { if (button == GLUT_LEFT_BUTTON && action == GLUT_DOWN && draw == true) { if (iPointNum == 0 || iPointNum == 2) { p[0].x = xMouse; p[0].y = winHeight - yMouse; iPointNum = 1; cout << "鼠标点击，开始绘制\n" <<endl; } else { cout << "鼠标点击，结束绘制\n" <<endl; if(square == false){ p[1].x = xMouse; p[1].y = winHeight - yMouse; iPointNum = 2; glutPostRedisplay(); } else { iPointNum = 2; glutPostRedisplay(); } } } } void PassiveMouseMove(GLint xMouse, GLint yMouse) { if(iPointNum == 1 && draw == true) { if(square == false){ p[1].x = xMouse; p[1].y = winHeight-yMouse; glutPostRedisplay(); } else{ p[1].x = xMouse; p[1].y = winHeight-yMouse; int s = abs(p[1].x-p[0].x); int l = abs(p[1].y-p[0].y); if(s != l){ s = s<l ? s : l; if(p[1].x <= p[0].x && p[1].y <= p[0].y){ p[1].x = p[0].x - s; p[1].y = p[0].y - s; } else if(p[1].x <= p[0].x && p[1].y > p[0].y){ p[1].x = p[0].x - s; p[1].y = p[0].y + s; } else if(p[1].x > p[0].x && p[1].y <= p[0].y){ p[1].x = p[0].x + s; p[1].y = p[0].y - s; } else if(p[1].x > p[0].x && p[1].y > p[0].y){ p[1].x = p[0].x + s; p[1].y = p[0].y + s; } } glutPostRedisplay(); } } } void KeyBoard(unsigned char key, int xMouse, int yMouse){ if(key == 's' && glutGetModifiers() & GLUT_ACTIVE_SHIFT){ square = true; cout << "shift 按下，绘制正圆\n" << endl; } else{ square = false; cout << "shift 取消，绘制椭圆\n" << endl; } } int main(int argc, char* argv[]) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE); //使用双缓存及RGB模式 glutInitWindowPosition(100, 100); //指定窗口位置 glutInitWindowSize(600, 500); //指定窗口大小 glutCreateWindow("橡皮筋交互式椭圆绘制"); glutDisplayFunc(Display); glutReshapeFunc(ChangeSize); glutMouseFunc(MousePlot); glutPassiveMotionFunc(PassiveMouseMove); glutKeyboardFunc(KeyBoard); createMenus(); init(); glutMainLoop(); //启动主事件循环 return 0; }