1 //图像的灰度直方图
 2 //By MoreWindows (http://blog.csdn.net/MoreWindows)
 3 #include <opencv2/opencv.hpp>
 4 #include <opencv2/legacy/compat.hpp>
 5 using namespace std;
 6 #pragma comment(linker, "/subsystem:\"windows\" /entry:\"mainCRTStartup\"")
 7 void FillWhite(IplImage *pImage)
 8 {
 9     cvRectangle(pImage, cvPoint(0, 0), cvPoint(pImage->width, pImage->height), CV_RGB(255, 255, 255), CV_FILLED);
10 }
11 // 创建灰度图像的直方图
12 CvHistogram* CreateGrayImageHist(IplImage **ppImage)
13 {
14     int nHistSize = 256;
15     float fRange[] = {0, 255};  //灰度级的范围  
16     float *pfRanges[] = {fRange};  
17     CvHistogram *pcvHistogram = cvCreateHist(1, &nHistSize, CV_HIST_ARRAY, pfRanges);
18     cvCalcHist(ppImage, pcvHistogram);
19     return pcvHistogram;
20 }
21 // 根据直方图创建直方图图像
22 IplImage* CreateHisogramImage(int nImageWidth, int nScale, int nImageHeight, CvHistogram *pcvHistogram)
23 {
24     IplImage *pHistImage = cvCreateImage(cvSize(nImageWidth * nScale, nImageHeight), IPL_DEPTH_8U, 1);
25     FillWhite(pHistImage);
26 
27     //统计直方图中的最大直方块
28     float fMaxHistValue = 0;
29     cvGetMinMaxHistValue(pcvHistogram, NULL, &fMaxHistValue, NULL, NULL);
30 
31     //分别将每个直方块的值绘制到图中
32     int i;
33     for(i = 0; i < nImageWidth; i++)
34     {
35         float fHistValue = cvQueryHistValue_1D(pcvHistogram, i); //像素为i的直方块大小
36         int nRealHeight = cvRound((fHistValue / fMaxHistValue) * nImageHeight);  //要绘制的高度
37         cvRectangle(pHistImage,
38             cvPoint(i * nScale, nImageHeight - 1),
39             cvPoint((i + 1) * nScale - 1, nImageHeight - nRealHeight),
40             cvScalar(i, 0, 0, 0), 
41             CV_FILLED
42         ); 
43     }
44     return pHistImage;
45 }
46 int main( int argc, char** argv )
47 {    
48     const char *pstrWindowsSrcTitle = "原图(http://blog.csdn.net/MoreWindows)";
49     const char *pstrWindowsGrayTitle = "灰度图(http://blog.csdn.net/MoreWindows)";
50     const char *pstrWindowsHistTitle = "直方图(http://blog.csdn.net/MoreWindows)";
51 
52     // 从文件中加载原图
53     IplImage *pSrcImage = cvLoadImage("007.jpg", CV_LOAD_IMAGE_UNCHANGED);
54     IplImage *pGrayImage = cvCreateImage(cvGetSize(pSrcImage), IPL_DEPTH_8U, 1);
55     // 灰度图
56     cvCvtColor(pSrcImage, pGrayImage, CV_BGR2GRAY);
57 
58     // 灰度直方图
59     CvHistogram *pcvHistogram = CreateGrayImageHist(&pGrayImage);
60     
61     // 创建直方图图像
62     int nHistImageWidth = 255;
63     int nHistImageHeight = 150;  //直方图图像高度
64     int nScale = 2;            
65     IplImage *pHistImage = CreateHisogramImage(nHistImageWidth, nScale, nHistImageHeight, pcvHistogram);
66 
67     // 显示
68     cvNamedWindow(pstrWindowsSrcTitle, CV_WINDOW_AUTOSIZE);
69     cvNamedWindow(pstrWindowsGrayTitle, CV_WINDOW_AUTOSIZE);
70     cvNamedWindow(pstrWindowsHistTitle, CV_WINDOW_AUTOSIZE);
71     cvShowImage(pstrWindowsSrcTitle, pSrcImage);
72     cvShowImage(pstrWindowsGrayTitle, pGrayImage);
73     cvShowImage(pstrWindowsHistTitle, pHistImage);
74 
75 
76     cvWaitKey(0);
77 
78     cvReleaseHist(&pcvHistogram);
79 
80     cvDestroyWindow(pstrWindowsSrcTitle);
81     cvDestroyWindow(pstrWindowsGrayTitle);
82     cvDestroyWindow(pstrWindowsHistTitle);
83     cvReleaseImage(&pSrcImage);
84     cvReleaseImage(&pGrayImage);
85     cvReleaseImage(&pHistImage);
86     return 0;
87 }