OpenCV 直方图计算

 

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

using namespace std;
using namespace cv;

/** @函数 main */
int main( int argc, char** argv )
{
  Mat src, dst;

 /// 装载图像
 src = imread( argv[1], 1 );

 if( !src.data )
   { return -1; }

 /// 分割成3个单通道图像 ( R, G 和 B )
 vector<Mat> rgb_planes;
 split( src, rgb_planes );

 /// 设定bin数目
 int histSize = 255;

 /// 设定取值范围 ( R,G,B) )
 float range[] = { 0, 255 } ;
 const float* histRange = { range };

 bool uniform = true; bool accumulate = false;

 Mat r_hist, g_hist, b_hist;

 /// 计算直方图:
 calcHist( &rgb_planes[0], 1, 0, Mat(), r_hist, 1, &histSize, &histRange, uniform, accumulate );
 calcHist( &rgb_planes[1], 1, 0, Mat(), g_hist, 1, &histSize, &histRange, uniform, accumulate );
 calcHist( &rgb_planes[2], 1, 0, Mat(), b_hist, 1, &histSize, &histRange, uniform, accumulate );

 // 创建直方图画布
 int hist_w = 400; int hist_h = 400;
 int bin_w = cvRound( (double) hist_w/histSize );

 Mat histImage( hist_w, hist_h, CV_8UC3, Scalar( 0,0,0) );

 /// 将直方图归一化到范围 [ 0, histImage.rows ]
 normalize(r_hist, r_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );
 normalize(g_hist, g_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );
 normalize(b_hist, b_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );

 /// 在直方图画布上画出直方图
 for( int i = 1; i < histSize; i++ )
   {
     line( histImage, Point( bin_w*(i-1), hist_h - cvRound(r_hist.at<float>(i-1)) ) ,
                      Point( bin_w*(i), hist_h - cvRound(r_hist.at<float>(i)) ),
                      Scalar( 0, 0, 255), 2, 8, 0  );
     line( histImage, Point( bin_w*(i-1), hist_h - cvRound(g_hist.at<float>(i-1)) ) ,
                      Point( bin_w*(i), hist_h - cvRound(g_hist.at<float>(i)) ),
                      Scalar( 0, 255, 0), 2, 8, 0  );
     line( histImage, Point( bin_w*(i-1), hist_h - cvRound(b_hist.at<float>(i-1)) ) ,
                      Point( bin_w*(i), hist_h - cvRound(b_hist.at<float>(i)) ),
                      Scalar( 255, 0, 0), 2, 8, 0  );
    }

 /// 显示直方图
 namedWindow("calcHist Demo", CV_WINDOW_AUTOSIZE );
 imshow("calcHist Demo", histImage );

 waitKey(0);

 return 0;

}