调整图像的亮度和对比度

简单原理：

为输出图像，为输入图像。其中用于调节对比度，增益用于调节亮度

实现代码：

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

using namespace cv;
int main(int argc, char** argv)
{
	Mat src, dst;
	src = imread("1.jpg");
	if (!src.data)
	{
		printf("cout not load image.../n");
		return -1;
	}
	char input_win[] = "input image";
	namedWindow(input_win, CV_WINDOW_AUTOSIZE);
	imshow(input_win, src);
	int height = src.rows;//高度
	int width = src.cols;//宽度
	//和输入图像的大小是一样的
	dst = Mat::zeros(src.size(), src.type());
	float alpha = 1.5;
	float beta = 30;
	for (int row = 0; row < height; row++)
	{
		for (int col = 0; col < width; col++)
		{
			//判断通道数，3通道，读取进到的是BGR图片
			if (src.channels() == 3)
			{
				//图像的数据是uchar类型，所以使用的是Vec3b
				//获取每隔通道的像素值
				float b = src.at<Vec3b>(row, col)[0];
				float g = src.at<Vec3b>(row, col)[1];
				float r = src.at<Vec3b>(row, col)[2];
				//然后利用已经获取到的像素值在像素位置进行操作
				dst.at<Vec3b>(row, col)[0] = saturate_cast<uchar>(b*alpha + beta);
				dst.at<Vec3b>(row, col)[1] = saturate_cast<uchar>(g*alpha + beta);
				dst.at<Vec3b>(row, col)[2] = saturate_cast<uchar>(r*alpha + beta);
			}
			//判断通道数，单通道灰度图
			else if (src.channels() == 1)
			{
				float v = src.at<uchar>(row, col);
				dst.at<uchar>(row, col) = saturate_cast<uchar>(v*alpha + beta);
			}
		}
	}
	char output_title[] = "contrast and brightness change demo";
	namedWindow(output_title, CV_WINDOW_AUTOSIZE);

	imshow(output_title, dst);
	waitKey(0);
	return 0;
} 

输出图像：

当然，我还可以使用src.convetTo将图片数据修改为CV_32F类型，然后读取各个通道像素值的时候就可以使用Vec3f进行读取了

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

using namespace cv;
int main(int argc, char** argv)
{
	Mat src, dst;
	src = imread("1.jpg");
	if (!src.data)
	{
		printf("cout not load image.../n");
		return -1;
	}
	char input_win[] = "input image";
	namedWindow(input_win, CV_WINDOW_AUTOSIZE);
	imshow(input_win, src);
	int height = src.rows;
	int width = src.cols;
	dst = Mat::zeros(src.size(), src.type());
	float alpha = 1.5;
	float beta = 30;

	//先对图像数据进行转换
	Mat m1;
	src.convertTo(m1, CV_32F);

	for (int row = 0; row < height; row++)
	{
		for (int col = 0; col < width; col++)
		{
			if (src.channels() == 3)
			{
				//此处使用的是m1的数据类型，m1是src转换后的图像数据类型
				float b = m1.at<Vec3f>(row, col)[0];
				float g = m1.at<Vec3f>(row, col)[1];
				float r = m1.at<Vec3f>(row, col)[2];

				dst.at<Vec3b>(row, col)[0] = saturate_cast<uchar>(b*alpha + beta);
				dst.at<Vec3b>(row, col)[1] = saturate_cast<uchar>(g*alpha + beta);
				dst.at<Vec3b>(row, col)[2] = saturate_cast<uchar>(r*alpha + beta);
			}
			else if (src.channels() == 1)
			{
				float v = src.at<uchar>(row, col);
				dst.at<uchar>(row, col) = saturate_cast<uchar>(v*alpha + beta);
			}
		}
	}
	char output_title[] = "contrast and brightness change demo";
	namedWindow(output_title, CV_WINDOW_AUTOSIZE);

	imshow(output_title, dst);
	waitKey(0);
	return 0;
} 

输出：同上输出.