【练习4.2】使用鼠标事件获取图片像素值

《学习OpenCV》中文版第4章第2题

题目要求：

点击图片是获取该点的颜色值，并在图像上点击鼠标处用文本将颜色值显示出来。

程序代码：

 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 }

【练习4.2】使用鼠标事件获取图片像素值