C和opencv实现图像显示图像的直方图

在C语言中，可以使用OpenCV库来实现图像的直方图显示。具体步骤如下：

1. 加载图像

IplImage* img = cvLoadImage("image.jpg", CV_LOAD_IMAGE_GRAYSCALE);

2. 计算直方图

int histSize = 256;
float range[] = {0, 256};
const float* histRange = {range};
CvHistogram* hist = cvCreateHist(1, &histSize, CV_HIST_ARRAY, &histRange, 1);
cvCalcHist(&img, hist, 0, NULL);
cvNormalizeHist(hist, 1.0);

3. 绘制直方图

int histHeight = 256;
int histWidth = 512;
int binWidth = cvRound((double)histWidth/histSize);
IplImage* histImg = cvCreateImage(cvSize(histWidth, histHeight), 8, 1);
cvSet(histImg, cvScalarAll(255));
float* histData = cvGetHistValueData(hist);

for (int i = 0; i < histSize; i++)
{
    int val = cvRound(histData[i]*histHeight);
    cvRectangle(histImg, cvPoint(i*binWidth, histHeight),
                cvPoint((i+1)*binWidth, histHeight-val),
                cvScalarAll(0), -1);
}

cvShowImage("Histogram", histImg);

完整代码如下：

#include <cv.h>
#include <highgui.h>

int main()
{
    IplImage* img = cvLoadImage("image.jpg", CV_LOAD_IMAGE_GRAYSCALE);
    int histSize = 256;
    float range[] = {0, 256};
    const float* histRange = {range};
    CvHistogram* hist = cvCreateHist(1, &histSize, CV_HIST_ARRAY, &histRange, 1);
    cvCalcHist(&img, hist, 0, NULL);
    cvNormalizeHist(hist, 1.0);
    int histHeight = 256;
    int histWidth = 512;
    int binWidth = cvRound((double)histWidth/histSize);
    IplImage* histImg = cvCreateImage(cvSize(histWidth, histHeight), 8, 1);
    cvSet(histImg, cvScalarAll(255));
    float* histData = cvGetHistValueData(hist);

    for (int i = 0; i < histSize; i++)
    {
        int val = cvRound(histData[i]*histHeight);
        cvRectangle(histImg, cvPoint(i*binWidth, histHeight),
                    cvPoint((i+1)*binWidth, histHeight-val),
                    cvScalarAll(0), -1);
    }

    cvShowImage("Histogram", histImg);
    cvWaitKey(0);

    cvReleaseImage(&img);
    cvReleaseImage(&histImg);
    cvReleaseHist(&hist);

    return 0;
}