计算并绘制单通道图像的直方图。在MATLAB中绘制直方图是一件非常简单的事情，可是到了C环境下，竟然变成了一个问题。各种实现方法都有，而且要自己动手重新编程。幸好有了OPENCV。下面的代码要求OPENCV4.0的支持，并在VC6中编译通过。
转自阿须数码//
// 对单通道图像做直方图
//
#include "cv.h"
#include "highgui.h"
#include <stdio.h>
#include <ctype.h>
int main( int argc, char** argv )
{
IplImage *src = 0;
IplImage *histimg = 0;
CvHistogram *hist = 0;
int hdims = 50; // 划分HIST的个数，越高越精确
float hranges_arr[] = {0,255};
float* hranges = hranges_arr;
int bin_w;
float max_val;
int i;
if( argc != 2 || (src=cvLoadImage(argv[1], 0)) == NULL) // force to gray image
return -1;
cvNamedWindow( "Histogram", 1 );
hist = cvCreateHist( 1, &hdims, CV_HIST_ARRAY, &hranges, 1 ); // 计算直方图
histimg = cvCreateImage( cvSize(320,200), 8, 3 );
cvZero( histimg );
cvCalcHist( &src, hist, 0, 0 ); // 计算直方图
cvGetMinMaxHistValue( hist, 0, &max_val, 0, 0 ); // 只找最大值
cvConvertScale( hist->bins, hist->bins, max_val ? 255. / max_val : 0., 0 ); // 缩放 bin 到区间 [0,255]
cvZero( histimg );
bin_w = histimg->width / hdims; // hdims: 条的个数，则 bin_w 为条的宽度
// 画直方图
for( i = 0; i < hdims; i++ )
{
double val = ( cvGetReal1D(hist->bins,i)*histimg->height/255 );
CvScalar color = CV_RGB(255,255,0); //(hsv2rgb(i*180.f/hdims);
cvRectangle( histimg, cvPoint(i*bin_w,histimg->height),
cvPoint((i+1)*bin_w,(int)(histimg->height - val)),
color, 1, 8, 0 );
}
cvShowImage( "Histogram", histimg );
cvWaitKey(0);
cvDestroyWindow("Histogram");
cvReleaseImage( &src );
cvReleaseImage( &histimg );
cvReleaseHist ( &hist );
return 0;
}
