通过对Mat遍历修改图像亮度和对比度与convertTo性能对比

通过对Mat遍历修改图像亮度和对比度与convertTo性能对比

g(i,j) = a*f(i,j) +b;
a 1.0~3.0(对比)  b 0~100(亮度)
sature_cast<uchar> 防止溢出



#include<stdio.h>
#include <opencv2/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>
using namespace cv;
void PrintMs(const char *text = "")
{
    static long long last = 0;
    long long cur = getTickCount();
    if (last == 0)
    {
        last = cur;
        return;
    }
    long long ms = 0;
    ms = ((double)(cur - last) / getTickFrequency()) * 1000;
    if (*text != 0)
    {
        printf("%s = %dms\n ", text, ms);
    }
    last = getTickCount();
}
//自己实现
void ChangeGain(Mat &src, Mat &des,float a, int b)
{
    des.create(src.size(), src.type());
    for (int r = 0; r < src.rows; r++)
    {
        for (int c = 0; c < src.cols; c++)
        {
            for (int i = 0; i < 3; i++)
            {
                des.at<Vec3b>(r, c)[i] =saturate_cast<uchar>(a*src.at<Vec3b>(r, c)[i] + b);

            }
        }
    }
}
int main(int argc, char *argv)
{
    //调整对比度和亮度
    Mat src = imread("lena.jpg");
    Mat des;
    PrintMs("");
    ChangeGain(src, des, 2.0, 50);
    PrintMs("Cahngegain");

    Mat des2;
    PrintMs("");
    //opencv自带函数
    //-1表示与原图类型一致
    src.convertTo(des2, -1, 2.0, 50);//性能好
    PrintMs("convertTo");
    namedWindow("src");
    namedWindow("des");
    namedWindow("des");
    imshow("src", src);
    imshow("des", des);
    imshow("des2", des2);

    waitKey(0);

    return 0;
}