笔记：OpenCV 读取摄像头并显示图像的R、G、B三个通道的直方图

要点：

1、读取摄像头

2、从一副彩色图像中分离出R、G、B三个通道（cvSplit）

3.  分别对每个通道图像创建直方图，并显示

源码如下：

// 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255cvSet(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;}

效果如下：