只需10分钟，获得一块神奇的电子表

虽然OpenCV的绘图函数不少时候能帮上忙，它们毕竟终究只是配角。直到看到外国友人的一篇blog，我沉默了。

将其代码拿出来跑效果是这样的（.gif）：

只能说，人有多大胆，地有多大产。

其实实现方法也很简单，调用系统的时间，利用三角函数转化成角度，再用OpenCV的绘图函数将钟画出来，更准确地说，是一帧一帧把指针画上去，画一遍擦一遍。

以下是代码，供参考：

#include <iostream>#include "opencv2/highgui/highgui.hpp"#include "opencv2/imgproc/imgproc_c.h"#include "opencv2/imgproc/imgproc.hpp"#include <stdio.h>#include <time.h>#include <sys/timeb.h>#include <sys/time.h>using namespace std;using namespace cv;int main(){    Mat clk(640,640,CV_8UC3); //Mat to store clock image    Mat back_up(640,640,CV_8UC3); //Mat to store backup image        Point cent(320,320);    Point perim(320,0);    int rad =320;    float sec_angle=270;    float min_angle=330;    float hour_angle=210;                //Draw second markings    int s1[60][2]={{320,25},{351,27},{381,31},{411,39},{440,51},{468,65},{493,81},{517,101},{539,123}, \        {559,147},{575,173},{589,200},{601,229},{609,259},{613,289},{615,320},{613,351},{609,381},{601,411}, \        {589,440},{575,468},{559,493},{539,517},{517,539},{493,559},{468,575},{440,589},{411,601},{381,609}, \        {351,613},{320,615},{289,613},{259,609},{229,601},{200,589},{173,575},{147,559},{123,539},{101,517}, \        {81,493},{65,468},{51,440},{39,411},{31,381},{27,351},{25,320},{27,289},{31,259},{39,229},{51,200}, \        {65,173},{81,147},{101,123},{123,101},{147,81},{172,65},{200,51},{229,39},{259,31},{289,27},};            int s2[60][2]={{320,5},{353,7},{385,12},{417,20},{448,32},{478,47},{505,65},{531,86},{554,109}, \        {575,135},{593,163},{608,192},{620,223},{628,255},{633,287},{635,320},{633,353},{628,385},{620,417}, \        {608,448},{593,478},{575,505},{554,531},{531,554},{505,575},{478,593},{448,608},{417,620},{385,628}, \        {353,633},{320,635},{287,633},{255,628},{223,620},{192,608},{163,593},{135,575},{109,554},{86,531}, \        {65,505},{47,478},{32,448},{20,417},{12,385},{7,353},{5,320},{7,287},{12,255},{20,223},{32,192}, \        {47,163},{65,135},{86,109},{109,86},{135,65},{162,47},{192,32},{223,20},{255,12},{287,7}};        for(int i=0;i<60;i++){        line(clk,Point(s1[i][0],s1[i][1]),Point(s2[i][0],s2[i][1]), Scalar(0,255,0,0), 1.5,CV_AA,0);    }            //Draw hour markings    int h1[12][2]={{320,45},{458,82},{558,183},{595,320},{558,458},{458,558},{320,595},{183,558}, \        {82,458},{45,320},{82,183},{182,82}};    int h2[12][2]={{320,5},{478,47},{593,163},{635,320},{593,478},{478,593},{320,635},{163,593}, \        {47,478},{5,320},{47,163},{162,47}};        for(int i=0;i<12;i++){        line(clk,Point(h1[i][0],h1[i][1]),Point(h2[i][0],h2[i][1]), Scalar(0,255,0,0), 4,CV_AA,0);    }        circle(clk,cent,rad-5,Scalar(0,0,255,0),4,CV_AA,0); //Dreaw outercircle of clock    circle(clk,cent,1,Scalar(0,255,0,0),5,CV_AA,0); //Draw inner circle        back_up=clk.clone(); // Clone to backup image        time_t rawtime;    struct tm * timeinfo;    float second;    float minute;    float hour;    float millisec;    struct timeb tmb;            while(1){        //Access system time and store to local variable        ftime(&tmb);        rawtime=tmb.time;        timeinfo = localtime ( &rawtime );                second     = timeinfo->tm_sec;        minute     = timeinfo->tm_min;        hour       = timeinfo->tm_hour;        millisec   = tmb.millitm;//毫秒                        second=second+millisec/1000;        sec_angle=(second*6)+270; //Convert second to angle                minute=minute+second/60;        min_angle=minute*6+270; //Conver minute to angle                if(hour>12)hour = hour-12;        hour_angle=(hour*30)+(minute*.5)+270; //Conver hour to angle                        if(sec_angle>360)sec_angle=sec_angle-360;        if(min_angle>360)min_angle=min_angle-360;        if(hour_angle>360)hour_angle=hour_angle-360;                //Fond out the co-ordinates in the circle perimeter for second and draw the line from center        perim.x =  (int)round(cent.x + (rad-5) * cos(sec_angle * CV_PI / 180.0));        perim.y =  (int)round(cent.y + (rad-5) * sin(sec_angle * CV_PI / 180.0));        line(clk,cent,perim, Scalar(0,255,255,0), 1.5,CV_AA,0);                        //Fond out the co-ordinates on the circle perimeter for minute and draw the line from center        perim.x =  (int)round(cent.x + (rad-50) * cos(min_angle * CV_PI / 180.0));        perim.y =  (int)round(cent.y + (rad-50) * sin(min_angle * CV_PI / 180.0));        line(clk,cent,perim, Scalar(0,255,255,0), 4,CV_AA,0);                        //Fond out the co-ordinates on the circle perimeter for hour and draw the line from center        perim.x =  (int)round(cent.x + (rad-75) * cos(hour_angle * CV_PI / 180.0));        perim.y =  (int)round(cent.y + (rad-75) * sin(hour_angle * CV_PI / 180.0));        line(clk,cent,perim, Scalar(0,255,255,0), 8,CV_AA,0);                        imshow("Clock",clk); //Show result in a window        clk.setTo(0); // set clk image to zero for next drawing        clk=back_up.clone(); // Clone the previously drawned markings from back-up image                char c=waitKey(10); // Wait for few millisecond and go back to loop.        if(c==27)break;    }        return 0;}