Opencv2.4学习：：灰度直方图

 实现代码：

#include<opencv2/imgproc/imgproc.hpp>
#include<opencv2/highgui/highgui.hpp>
#include<iostream>
using namespace std;
using namespace cv;
int main()
{
	Mat srcImage = imread("F:\\opencv_re_learn\\2.jpg");
	if (!srcImage.data){
		cout << "failed to read" << endl;
		system("pause");
		return -1;
	}
	imshow("srcImage", srcImage);
	//conver to gray
	Mat srcGray;
	cvtColor(srcImage, srcGray, CV_BGR2GRAY);
	//定义直方图参数
	const int channels[1] = { 0 };
	const int histSize[1] = { 256 };
	float pranges[2] = { 0, 255 };
	const float* ranges[1] = { pranges };
	MatND hist;
	//计算直方图
	calcHist(&srcGray, 1, channels, Mat(),
		hist, 1, histSize, ranges);
	//将直方图绘制
	//初始化画布参数
	int hist_w = 500;
	int hist_h = 500;
	int nHistSize = 255;
	//区间
	int bin_w = cvRound((double)hist_w / nHistSize);
	//定义全黑背景
	Mat histImage(hist_w, hist_h, CV_8UC3, Scalar(0, 0, 0));
	//直方图归一化到【0，histImage.rows】
	normalize(hist, hist, 0, histImage.rows,
		NORM_MINMAX, -1, Mat());
	//在画出直方图
	for (int i =0; i < nHistSize; i++){
		/*line(histImage, Point(bin_w*(i - 1),
			hist_h - cvRound(hist.at<float>(i - 1))),
			Point(bin_w*(i),
			hist_h - cvRound(hist.at<float>(i))),
			Scalar(0, 0, 255), 2, 8, 0);*/
		for (int j = 0; j <= cvRound(hist.at<float>(i)); j++){
			line(histImage, Point(bin_w*(i),hist_h-j),
				Point(bin_w*(i), hist_h-(j + 1)),
				Scalar(255, 255, 255), 2, 8, 0);
		}
	}
	//显示直方图
	imshow("histImage", histImage);
	waitKey(0);
	return 0;
	waitKey(0);
	return 0;
}