C++實作遙感圖像2%線性拉伸

1.接口函數

cv::Mat ColorImageStretch(const cv::Mat img, const float ratio)
{
	//影像分RGB計算灰階直方圖
	cv::Mat mimg = img.clone();
	cv::Mat bgr[3];
	split(mimg, bgr);
	std::vector<cv::Point2f> hb = IS_Histogram(bgr[0]);
	std::vector<cv::Point2f> hg = IS_Histogram(bgr[1]);
	std::vector<cv::Point2f> hr = IS_Histogram(bgr[2]);
	//統計直方圖累計頻率ratio值對應的灰階
	uint minb = IS_MinRatio(hb, ratio);
	uint ming = IS_MinRatio(hg, ratio);
	uint minr = IS_MinRatio(hr, ratio);
	uint maxb = IS_MaxRatio(hb, ratio);
	uint maxg = IS_MaxRatio(hg, ratio);
	uint maxr = IS_MaxRatio(hr, ratio);
	//開始拉伸工作
	cv::Mat b, g, r;
	b = IS_StretchDeal(bgr[0], minb, maxb);
	g = IS_StretchDeal(bgr[1], ming, maxg);
	r = IS_StretchDeal(bgr[2], minr, maxr);
	//合并拉伸結果
	cv::Mat newbgr;
	newbgr.create(img.rows, img.cols, CV_32FC3);
	cv::Mat nbgr[3] = { b, g, r };
	merge(nbgr, 3, newbgr);
	return newbgr;
}
           

2.子函數

std::vector<cv::Point2f> IS_Histogram(const cv::Mat img)
{
	cv::Mat mimg = img.clone();
	int rows = mimg.rows;
	int cols = mimg.cols;
	//統計每個灰階出現的次數
	std::vector<long int> hisnum(256);
	for (int i(0); i < rows; ++i)
	{
		for (int j(0); j < cols; ++j)
		{
			uint gv = mimg.at<uchar>(i, j);
			++hisnum[gv];
		}
	}
	//開始計算灰階頻率
	long int pnum = rows * cols;
	std::vector<cv::Point2f> hisp;
	for (int i(0); i < hisnum.size(); ++i)
	{
		float p = (float)hisnum[i] / pnum;
		hisp.push_back(cv::Point2f(i, p));
	}
	return hisp;
}
           

uint IS_MinRatio(const std::vector<cv::Point2f> 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;
}
           

uint IS_MaxRatio(const std::vector<cv::Point2f> 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;
}
           

cv::Mat IS_StretchDeal(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);
	//歸一化參數
	float dertnum = maxnum - minnum;
	//開始處理
	for (int i(0); i < rows; ++i)
	{
		for (int j(0); j < cols; ++j)
		{
			uint a = mimg.at<uchar>(i, j);
			//小于ratio對應像素值取0
			if (a <= minnum)
				nimg.at<uchar>(i, j) = 0;
			//大于ratio值對應像素值取255
			else if (a >= maxnum)
				nimg.at<uchar>(i, j) = 255;
			//中間值拉伸到0-255
			else
				nimg.at<uchar>(i, j) = 255 * (mimg.at<uchar>(i, j) - minnum) / dertnum;
		}
	}
	return nimg;
}