c++实现ENVI1%Liner、2%Liner等拉伸

在参考了博主遥感服务提供的思路后，进行该思路的实现，注意：目前只能实现tif或png格式拉伸，主要代码如下：

Cstretch函数：

cv::Mat CStretch(const cv::Mat img, const float ratio)
{
	//影像分RGB计算灰度直方图
	cv::Mat mimg = img.clone();
	cv::Mat bgr[3];
	split(mimg, bgr);
	std::vector hb = CHistogram(bgr[0]);
	std::vector hg = CHistogram(bgr[1]);
	std::vector hr = CHistogram(bgr[2]);
	//统计直方图累计频率ratio值对应的灰度
	uint minb = MinRatio(hb, ratio);
	uint ming = MinRatio(hg, ratio);
	uint minr = MinRatio(hr, ratio);
	uint maxb = MaxRatio(hb, ratio);
	uint maxg = MaxRatio(hg, ratio);
	uint maxr = MaxRatio(hr, ratio);
	//开始拉伸工作
	cv::Mat b, g, r;
	b = CStretchDeal(bgr[0], minb, maxb);
	g = CStretchDeal(bgr[1], ming, maxg);
	r = CStretchDeal(bgr[2], minr, maxr);
	//合并拉伸结果
	cv::Mat newbgr;
	newbgr.create(img.rows, img.cols, CV_32FC3);
	cv::Mat nbgr[3] = { b, g, r };
	merge(nbgr, 3, newbgr);
	return newbgr;
}

CHistogram函数：

std::vector CHistogram(const cv::Mat img)
{
	cv::Mat mimg = img.clone();
	int rows = mimg.rows;
	int cols = mimg.cols;
	//统计每个灰度出现的次数
	std::vector hisnum(256);
	for (int i(0); i < rows; ++i)
	{
		for (int j(0); j < cols; ++j)
		{
			uint gv = mimg.at(i, j);
			++hisnum[gv];
		}
	}
	//开始计算灰度频率
	long int pnum = rows * cols;
	std::vector hisp;
	for (int i(0); i < hisnum.size(); ++i)
	{
		float p = (float)hisnum[i] / pnum;
		hisp.push_back(cv::Point2f(i, p));
	}
	return hisp;
}

MinRatio函数：

uint MinRatio(const std::vector data, const float ratio)
{
	float minp(0);
	uint outnum(0);
	for (int i(0); i < data.size(); ++i)
	{
		minp += data[i].y;
		if (minp >= ratio)
		{
			outnum = i;
			break;
		}
	}
	return outnum;
}

MaxRatio函数：

uint MaxRatio(const std::vector data, const float ratio)
{
	float maxp(0);
	uint outnum(0);
	for (int i(data.size() - 1); i >= 0; --i)
	{
		maxp += data[i].y;
		if (maxp >= ratio)
		{
			outnum = i;
			break;
		}
	}
	return outnum;
}

CStretchDeal函数：

cv::Mat CStretchDeal(const cv::Mat img, const uint minnum, const uint maxnum)
{
	cv::Mat mimg = img.clone();
	int rows = mimg.rows;
	int cols = mimg.cols;
	cv::Mat nimg = cv::Mat::zeros(rows, cols, CV_8U);
	//归一化参数
	float dertnum = maxnum - minnum;
	//开始处理
	for (int i(0); i < rows; ++i)
	{
		for (int j(0); j < cols; ++j)
		{
			uint a = mimg.at(i, j);
			//小于ratio对应像素值取0
			if (a <= minnum)
				nimg.at(i, j) = 0;
			//大于ratio值对应像素值取255
			else if (a >= maxnum)
				nimg.at(i, j) = 255;
			//中间值拉伸到0-255
			else
				nimg.at(i, j) = 255*(mimg.at(i, j) - minnum) / dertnum;
		}
	}
	return nimg;
}

调用测试：

#include
#include
int main()
{
        //影像路径
        string imgfile = "F:/groundationproject/PicturesCut2000+2000SameLeftTopAll/f1.tif";
	cv::Mat oimg = cv::imread(imgfile);
	//show原图
	cv::namedWindow("before stretch", 0);
	cv::imshow("before stretch", oimg);
	//拉伸
	cv::Mat nimg = CStretch(oimg, 0.01);
	//show新图
	cv::namedWindow("after stretch", 0);
	cv::imshow("after stretch", nimg);
	cv::waitKey();
}

拉伸效果展示：

参考文献：

影像linear 2%实现