opencv学习之（五）-直方图计算和绘制图像直方图

1 直方图

灰度直方图的定义

2 灰度直方图的计算

// Histogram.cpp : 定义控制台应用程序的入口点。
//

/***********************************************************************
 * OpenCV 2.4.4 测试例程
 * 杜健健 提供
 ***********************************************************************/

#include "stdafx.h"
#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>

using namespace std;
using namespace cv;

//参数：Gray_img --输入的灰度图像
//      hist 计算后输出的直方图
void myCal_Hist(Mat Gray_img,MatND hist){

	int bins = 256;  
    int hist_size[] = {bins};  
    float range[] = { 0, 256 };  
    const float* ranges[] = { range};  

	int channels[] = {0};  
    //计算直方图
    calcHist( &Gray_img, 1, channels, Mat(), // do not use mask  
        hist, 1, hist_size, ranges,  
        true, // the histogram is uniform  
        false );  

	//绘制直方图图像
	int hist_height=256;  
	//int bins = 256;
	double max_val;  //直方图的最大值
	int scale = 2;   //直方图的宽度
    minMaxLoc(hist, 0, &max_val, 0, 0); //计算直方图最大值

    Mat hist_img = Mat::zeros(hist_height,bins*scale, CV_8UC3); //创建一个直方图图像并初始化为0 

	cout<<"max_val = "<<max_val<<endl;
    //在直方图图像中写入直方图数据
    for(int i=0;i<bins;i++)  
    {  
        float bin_val = hist.at<float>(i); //	第i灰度级上的数	
        int intensity = cvRound(bin_val*hist_height/max_val);  //要绘制的高度  
		//填充第i灰度级的数据
        rectangle(hist_img,Point(i*scale,hist_height-1),  
            Point((i+1)*scale - 1, hist_height - intensity),  
            CV_RGB(255,255,255));  
    }
	
    imshow( "Gray Histogram2", hist_img );
}

//根据直方图数据绘制并显示直方图图像
void myShow_Histogram(MatND &hist,int scale){

	int hist_height=256;  
	int bins = 256;
	double max_val;  

    minMaxLoc(hist, 0, &max_val, 0, 0); 

    Mat hist_img = Mat::zeros(hist_height,bins*scale, CV_8UC3);  

	cout<<"max_val = "<<max_val<<endl;
    for(int i=0;i<bins;i++)  
    {  
        float bin_val = hist.at<float>(i); //

		
        int intensity = cvRound(bin_val*hist_height/max_val);  //要绘制的高度  

        rectangle(hist_img,Point(i*scale,hist_height-1),  
            Point((i+1)*scale - 1, hist_height - intensity),  
            CV_RGB(255,255,255));  
    }
	
    imshow( "Gray Histogram2", hist_img );
}

int _tmain(int argc, _TCHAR* argv[])
{

	Mat src,gray,src2,gray2;  
    //src=imread("D://input//buti.jpg");  
	src = imread("D://input//yalefaces//01//s1.bmp");
    cvtColor(src,gray,CV_RGB2GRAY);  //转换成灰度图

	src2 = imread("D://input//yalefaces//02//s1.bmp");
    cvtColor(src2,gray2,CV_RGB2GRAY);  //转换成灰度图
    MatND hist2;

    imshow( "Source", src );  
    //imshow( "Gray Histogram", hist_img );  
    imshow("Source2",src2);

	myCal_Hist(gray2,hist2);
	//myShow_Histogram(hist2,5);


    waitKey();  
    return 0;  
	
}

3 示例展示

4 参考

http://blog.csdn.net/xiaowei_cqu/article/details/7600666

http://blog.csdn.net/xiaowei_cqu/article/details/8833799#comments