OpenCV 读取摄像头并显示图像的R、G、B三个通道的直方图

// Camera_Capture_Histogram.cpp : Defines the entry point for the console application.
//author: JarvisChu
//date: 2012-1-14

#include "stdafx.h"
#include "opencv2/opencv.hpp"
#include <iostream>
using namespace std;

const char* pstrSrcWnd = "Src";
const char* pstrBHistWnd = "b plane";
const char* pstrGHistWnd = "g plane";
const char* pstrRHistWnd = "r plane";

//计算和绘制直方图（R,G,B）
/* img 通道图像
* hist_img: 直方图的绘图图像
* pstrWndName: 绘图窗口
*/
void draw_histogram(IplImage* img,IplImage* hist_img,const char* pstrWndName)
{

CvHistogram* hist = NULL;

int bin_count = 256;
float range[] = {0,255};
float* ranges[]={range};

hist = cvCreateHist(1,         //一维
&bin_count, //每一维上bin（直方柱）的个数， 此处为 256 【由上述两个参数，函数就会创建一个1*256的矩阵】
CV_HIST_ARRAY,
ranges,
1);
cvClearHist(hist);   //防止初始化时有其它数据，先清理一下

cvCalcHist(&img,hist,0,0);

//得到直方图的最值及标号
float min,max;
int min_idx,max_idx;
cvGetMinMaxHistValue(hist,&min,&max,&min_idx,&max_idx);

//cout<<"min: "<<min<<"  max:"<<max<<endl;
if(max == 0) {cout<<"max =0 err!"<<endl;max = 100;}

//缩放直方图的大小，和图像相适应
cvScale(hist->bins,hist->bins,((double)hist_img->height)/max,0);

//设置所有的直方图的数值为255
cvSet(hist_img,cvScalarAll(255),0);

// 平均每个直放柱的宽度
int bin_w=cvRound((double)hist_img->width/bin_count);

//画直方图
for(int i=0;i<bin_count;i++)
{
cvRectangle(hist_img,
cvPoint(i*bin_w,hist_img->height),  //左下角的点（i*bin_w，height）
cvPoint((i+1)*bin_w, hist_img->height-cvRound(cvGetReal1D(hist->bins,i))),//右上角的点((i+1)*bin_w,图像高度-直方柱的高度)
cvScalarAll(0),
-1,
8,
0);
}

//显示直方图
cvShowImage(pstrWndName,hist_img);
}
int _tmain(int argc, _TCHAR* argv[])
{
//创建窗口
cvNamedWindow(pstrSrcWnd,1);
cvNamedWindow(pstrBHistWnd,1);
cvNamedWindow(pstrGHistWnd,1);
cvNamedWindow(pstrRHistWnd,1);

//读取摄像头
CvCapture* capture = cvCreateCameraCapture(-1);
if(!capture) cout<<"无法打开摄像头"<<endl;

//读取一帧数据以获取参数
IplImage* frame = NULL;
frame = cvQueryFrame(capture);

//B G R 通道
CvSize img_size;img_size.width = frame->width;img_size.height = frame->height;
IplImage* b = cvCreateImage(img_size,8,1);
IplImage* g = cvCreateImage(img_size,8,1);
IplImage* r = cvCreateImage(img_size,8,1);

//直方图
CvSize size;size.width = 320;size.height = 200;
IplImage* b_hist_img = cvCreateImage(size,8,1);
IplImage* g_hist_img = cvCreateImage(size,8,1);
IplImage* r_hist_img = cvCreateImage(size,8,1);

while(1)
{
frame = cvQueryFrame(capture);
if(!frame) break;

//分割BGR通道
cvSplit(frame,b,g,r,0);

//显示摄像头图像
cvShowImage(pstrSrcWnd,frame);

//绘制直方图
draw_histogram(b,b_hist_img,pstrBHistWnd);
draw_histogram(g,g_hist_img,pstrGHistWnd);
draw_histogram(r,r_hist_img,pstrRHistWnd);

char c = cvWaitKey(330);
if(c == 27) break;
}

cvReleaseImage(&frame);
cvReleaseImage(&b);
cvReleaseImage(&g);
cvReleaseImage(&r);
cvReleaseImage(&b);
cvReleaseImage(&g);
cvReleaseImage(&r);
cvDestroyAllWindows();

return 0;
}

<img src="https://img-blog.csdn.net/20150907222045937" alt="" />