Opencv學習筆記（五） -------增強圖像的對比度和亮度

（一）理論

（二）重要的API
Mat dst = Mat::zeros(src.size(),src.type());創建一張與原圖像大小類型相同的空白圖像，初始值爲0；

Saturate_cast(數據) 確保數據在0~255之間

/*************獲取圖像像素值*************/
Mat.at<Vec3b>(row,col)[0]     //blue通道像素值   
Mat.at<Vec3b>(row,col)[1]    //green通道像素值
Mat.at<Vec3b>(row,col)[2]    //red通道像素值

Mat.at<uchar>(row,col)      //灰度圖像數值

（代碼部分）

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

using namespace cv;
using namespace std;

int main(int argc, char** argv)
{
	Mat src;
	src = imread("D:/picture/Curry.jpeg");

	if (src.empty())     //如果沒有找到圖片
	{
		printf("could not find picture.....\n");
		return -1;
	}

	//cvtColor(src, src, CV_BGR2GRAY);        //轉化成灰度圖

	namedWindow("input image", CV_WINDOW_AUTOSIZE);
	imshow("input image", src);

	Mat dst = src.zeros(src.size(), src.type());

	int height = src.rows;
	int weight = src.cols;
	
	double alpha = 2;
	double beta = 5;

	for (int row = 0; row < height; row++)
	{
		for (int col = 0; col < weight; col++)
		{
			if (src.channels() == 3)
			{
				int blue = src.at<Vec3b>(row, col)[0];
				int green = src.at<Vec3b>(row, col)[1];
				int red = src.at<Vec3b>(row, col)[2];

				dst.at<Vec3b>(row, col)[0] = saturate_cast<uchar>(blue * alpha + beta);
				dst.at<Vec3b>(row, col)[1] = saturate_cast<uchar>(green * alpha + beta);
				dst.at<Vec3b>(row, col)[2] = saturate_cast<uchar>(red * alpha + beta);
			}
			else if (src.channels() == 1)
			{
				int gray = src.at<uchar>(row, col);
				dst.at<uchar>(row,col) = saturate_cast<uchar>(gray * alpha + beta);
			}
		}
	}
	namedWindow("output image", CV_WINDOW_AUTOSIZE);
	imshow("output image", dst);

	waitKey(0);   //等待
	return 0;
}

實驗效果