图像处理之直方图均衡化拉伸

#include <iostream>
#include <opencv2\opencv.hpp>

using namespace std;
using namespace cv;

int main()
{
	Mat srcImage;
	srcImage = imread("D:\\Data\\imgDemo\\lena512color.bmp", IMREAD_GRAYSCALE);
	imshow("原图像", srcImage);
	
	Mat dstImage;
	equalizeHist(srcImage, dstImage);
	imshow("均衡后", dstImage);

	waitKey();

	return 0;
}

#include <iostream>
#include <algorithm>
#include <gdal_priv.h>

using namespace std;

//直方图均衡化
void GetHistAvgLut(GUIntBig* anHistogram, int HistNum, vector<uint8_t > &lut)
{
	//统计像素总的个数
	size_t sum = 0;
	for (int ci = 0; ci < HistNum; ci++)
	{
		sum = sum + anHistogram[ci];
	}

	//
	vector<double> funProbability(HistNum, 0.0); //概率密度函数
	vector<double> funProbabilityDistribution(HistNum, 0.0);	//概率分布函数

	//计算概率分布函数
	double dsum = (double)sum;
	double accumulation = 0;
	for (int ci = 0; ci < HistNum; ci++)
	{
		funProbability[ci] = anHistogram[ci] / dsum;
		accumulation = accumulation + funProbability[ci];
		funProbabilityDistribution[ci] = accumulation;
	}

	//归一化的值扩展为0~255的像素值，存到颜色映射表
	lut.resize(HistNum, 0);
	for (int ci = 0; ci < HistNum; ci++)
	{
		double value = std::min<double>(std::max<double>(255 * funProbabilityDistribution[ci], 0), 255);
		lut[ci] = (unsigned char)value;
	}
}

//计算16位的颜色映射表
bool CalImgLut(GDALDataset* img, vector<vector<uint8_t>>& lut)
{
	int bandNum = img->GetRasterCount();    //波段数
	lut.resize(bandNum);

	//
	for (int ib = 0; ib < bandNum; ib++)
	{
		//计算该通道的直方图
		int HistNum = 256;
		GUIntBig* anHistogram = new GUIntBig[HistNum];
		int bApproxOK = FALSE;
		img->GetRasterBand(ib + 1)->GetHistogram(-0.5, 255.5, HistNum, anHistogram, TRUE, bApproxOK, NULL, NULL);

		//直方图均衡化	
		GetHistAvgLut(anHistogram, HistNum, lut[ib]);

		//
		delete[] anHistogram;
		anHistogram = nullptr;
	}

	return true;
}


int main()
{
	//
	GDALAllRegister();          //GDAL所有操作都需要先注册格式
	CPLSetConfigOption("GDAL_FILENAME_IS_UTF8", "NO");  //支持中文路径

	//读取
	const char* imgPath = "D:\\Data\\imgDemo\\lena512color.bmp";
	GDALDataset* img = (GDALDataset *)GDALOpen(imgPath, GA_ReadOnly);
	if (!img)
	{
		cout << "Can't Open Image!" << endl;
		return 1;
	}

	//
	int imgWidth = img->GetRasterXSize();   //图像宽度
	int imgHeight = img->GetRasterYSize();  //图像高度
	int bandNum = img->GetRasterCount();    //波段数
	int depth = GDALGetDataTypeSize(img->GetRasterBand(1)->GetRasterDataType()) / 8;    //图像深度

	//创建颜色映射表
	vector<vector<uint8_t>> lut;
	CalImgLut(img, lut);

	//创建
	GDALDriver *pDriver = GetGDALDriverManager()->GetDriverByName("BMP"); //图像驱动
	char** ppszOptions = NULL;
	const char* dstPath = "D:\\Data\\imgDemo\\dst.bmp";
	int bufWidth = imgWidth;
	int bufHeight = imgHeight;
	GDALDataset* dst = pDriver->Create(dstPath, bufWidth, bufHeight, bandNum, GDT_Byte, ppszOptions);
	if (!dst)
	{
		printf("Can't Write Image!");
		return false;
	}

	//读取buf
	size_t imgBufNum = (size_t)bufWidth * bufHeight * bandNum * depth;
	GByte *imgBuf = new GByte[imgBufNum];
	img->RasterIO(GF_Read, 0, 0, bufWidth, bufHeight, imgBuf, bufWidth, bufHeight,
		GDT_Byte, bandNum, nullptr, bandNum*depth, bufWidth*bandNum*depth, depth);

	//迭代通过颜色映射表替换值
	for (int yi = 0; yi < bufHeight; yi++)
	{
		for (int xi = 0; xi < bufWidth; xi++)
		{
			for (int bi = 0; bi < bandNum; bi++)
			{
				size_t m = (size_t)bufWidth * bandNum * yi + bandNum * xi + bi;
				imgBuf[m] = lut[bi][imgBuf[m]];
			}
		}
	}
	
	//写入
	dst->RasterIO(GF_Write, 0, 0, bufWidth, bufHeight, imgBuf, bufWidth, bufHeight,
		GDT_Byte, bandNum, nullptr, bandNum*depth, bufWidth*bandNum*depth, depth);

	//释放
	delete[] imgBuf;
	imgBuf = nullptr;
	GDALClose(dst);
	dst = nullptr;
	GDALClose(img);
	img = nullptr;

	return 0;
}