【練習4.2】使用滑鼠事件擷取圖片像素值

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《學習OpenCV》中文版第4章第2題

題目要求：

點擊圖片是擷取該點的顏色值，並在映像上點擊滑鼠處用文本將顏色值顯示出來。

程式碼：

 1 #include "stdafx.h" 2 #include <cv.h> 3 #include <highgui.h> 4 using namespace std; 5 using namespace cv; 6  7 void MouseCallBack(int event, int x, int y, int flags, void *param); 8  9 int _tmain(int argc, _TCHAR* argv[])10 {11     const char * fileName = "D:\\Work\\Work_Programming\\Source\\Image\\lena.jpg"; 12     cvNamedWindow("MouseEvent", CV_WINDOW_AUTOSIZE);13     IplImage * img = cvLoadImage(fileName,1);14     assert(img);15 16     cvSetMouseCallback("MouseEvent", MouseCallBack, img);17 18     while (true)19     {20         cvShowImage("MouseEvent", img);21 22         if (waitKey(15) == 27)23         {24             break;25         }26     }    27     28     cvWaitKey(0);29 30     cvReleaseImage(&img);31     cvDestroyWindow("MouseEvent"); 32  33     //system("pause");34  35     return 0;36 }37 38 void MouseCallBack(int event, int x, int y, int flags, void *param)39 {40     IplImage * img = (IplImage *)param;41 42     CvFont font;43     cvInitFont(&font, CV_FONT_HERSHEY_SIMPLEX, 0.5, 0.5, 0, 2, 8);44 45     CvScalar scl;46     char * str = (char *)malloc(30 * sizeof(char));47 48     if (event == CV_EVENT_LBUTTONDOWN)49     {50         scl = cvGet2D(img, x, y);51 52         double b = scl.val[0];53         double g = scl.val[1];54         double r = scl.val[2];55         56         sprintf(str, "B:%.0f,G:%.0f,R:%.0f", b, g, r);57 58         cvPutText(img, str, cvPoint(x, y), &font, cvScalar(255, 0, 0));59     }60 61     free(str);62 }