3.6.2 编程实例－河南地图绘制

程序有关介绍请参考图书3.6.1节内容

程序运行结果如下图：

image

#include <iostream> #include <fstream> #include<vector> #include <GL/glut.h> using namespace std;

class MapPoint { public:     double longitude;     double latitude; }; class Polygon { public:     vector<MapPoint> points; //多边形的顶点序列 }; vector<Polygon*> polys; //多边形集合 vector<Polygon*> ReadMapData(char* filename) {     int PointCount;     vector<Polygon*> polygons;     ifstream fs(filename);     while(fs.eof()!=true)     {         Polygon* poly=new Polygon;         fs>>PointCount;         cout<<PointCount<<endl;         for(int i=0;i<PointCount;i++)         {             MapPoint p;             fs>>p.longitude>>p.latitude;             poly->points.push_back(p);         }         polygons.push_back(poly);

    }     return polygons; } void display(void) {        glClear (GL_COLOR_BUFFER_BIT);        //用蓝色色绘制各省边界     glColor3f (0.0, 0.0, 1.0);     glPolygonMode(GL_BACK, GL_LINE);         for(int i=0;i<polys.size();i++)     {                vector<MapPoint> points=polys[i]->points;         glBegin(GL_LINE_STRIP);         for(int j=0;j<points.size();j++)         {                        glVertex3f (points[j].longitude, points[j].latitude, 0.0);                }         glEnd();     }        glFlush(); } void init (void) {     //设置背景颜色     glClearColor (1.0, 1.0, 1.0, 0.0);     //初始化观察值     glMatrixMode(GL_PROJECTION);    //将矩阵模式设为投影     glLoadIdentity();                 //对矩阵进行单位化     glOrtho(110.0, 118.0, 30.0, 38.0, -1.0, 1.0);   //构造平行投影矩阵 } int main(int argc, char** argv) {     //数据文件请到http://files.cnblogs.com/opengl/HenanCounty.rar下载放到D盘根目录下并解压     char* filename="D:/HenanCounty.txt";

    polys=ReadMapData(filename);        glutInit(&argc, argv);     glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);  //单缓存和RGB     glutInitWindowSize (500, 500);     glutInitWindowPosition (100, 100);     glutCreateWindow ("地图绘制");     init ();     glutDisplayFunc(display);     //显示回调函数     glutMainLoop();     return 0; }