#include <iostream>
#include <opencv2/opencv.hpp>
using namespace std;
using namespace cv;


void stretch(Mat &src, Mat &dst, int nMin, int nMax)
{
	int low_value = nMin;    //拉伸後像素的最小值 
	int high_value = nMax;   //拉伸後像素的最大值

	float rate = 0;          //影象的拉伸率

	float stretch_p[256], stretch_p1[256], stretch_num[256];
	//清空三個陣列,初始化填充陣列元素為0
	memset(stretch_p, 0, sizeof(stretch_p));
	memset(stretch_p1, 0, sizeof(stretch_p1));
	memset(stretch_num, 0, sizeof(stretch_num));
	//統計影象各個灰度級出現的次數
	uchar* srcData = src.ptr<uchar>(0);
	uchar* dstData = dst.ptr<uchar>(0);
	//相當於c語言版本opencv的：
	//uchar* srcData = (uchar*)src->imageData;
	//uchar* dstData = (uchar*)dst->imageData;
	int nHeight = src.rows;
	int nWidth = src.cols;
	int i, j;
	uchar nVal = 0;
	for (i = 0; i<nHeight; i++)
	{
		for (j = 0; j<nWidth; j++)
		{
			nVal = srcData[i*nWidth + j];
			stretch_num[nVal]++;
		}
	}
	//統計各個灰度級出現的概率
	for (i = 0; i<256; i++)
	{
		stretch_p[i] = stretch_num[i] / (nHeight*nWidth);
	}
	//統計各個灰度級的概率和
	for (i = 0; i<256; i++)
	{
		for (j = 0; j <= i; j++)
		{
			stretch_p1[i] += stretch_p[j];
		}
	}
	//計算兩個閾值點的值
	for (i = 0; i<256; i++)
	{
		if (stretch_p1[i]<0.1)     //low_value取值接近於10%的總畫素的灰度值
		{
			low_value = i;
		}
		if (stretch_p1[i]>0.9)     //high_value取值接近於90%的總畫素的灰度值
		{
			high_value = i;
			break;
		}
	}
	rate = (float)255 / (high_value - low_value + 1);
	//進行灰度拉伸
	for (i = 0; i<nHeight; i++)
	{
		for (j = 0; j<nWidth; j++)
		{
			nVal = srcData[i*nWidth + j];
			if (nVal<low_value)
			{
				dstData[i*nWidth + j] = 0;
			}
			else if (nVal>high_value)
			{
				dstData[i*nWidth + j] = 255;
			}
			else
			{
				dstData[i*nWidth + j] = (uchar)((nVal - low_value)*rate + 0.5);
				if (dstData[i*nWidth + j]>255)
				{
					dstData[i*nWidth + j] = 255;
				}
			}
		}
	}
}


int main(int argc, char* argv[])
{
	Mat img = imread("11.bmp", 0);
	if (img.empty())
	{
		cout << "Error: Could not load image" << endl;
		return 0;
	}
	imshow("img", img);

	Mat dst = img.clone();

	//計算影象的最大最小值 最大值賦0，最小值賦255
	int pixMax = 0, pixMin = 255;
	uchar * pdata = NULL;
	for (size_t r = 0; r < img.rows; r++)
	{
		pdata = img.ptr<uchar>(r);
		for (size_t c = 0; c < img.cols; c++)
		{
			if (pdata[c] > pixMax)
				pixMax = pdata[c];
			if (pdata[c] < pixMin)
				pixMin = pdata[c];
		}
	}

	stretch(img, dst, pixMin, pixMax);
	imshow("dst", dst);
	waitKey();


	return 0;
}
 

效果沒有文章中的好，不知道他是怎麼做的