OpenCV --- 修改图像的对比度、亮度 、RGB转Gray图像、修改图像的尺寸

[code]#include <opencv2/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>
#include <iostream>
using namespace cv;
using namespace std;

// 计时函数
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();
}

// RGB图像转Gray图像
void RGBToGray(Mat &src, Mat &des)
{
// GRay = (R*30 + G*59 + B*11 +50)/100
des.create(src.rows,src.cols,CV_8UC1);
for (int r = 0; r < src.rows; r++)
{
for (int c = 0; c < src.cols; c++)
{
Vec3b &m = src.at<Vec3b>(r, c);
int gray = (m[2] * 30 + m[1] * 59 + m[0] * 11 + 50) / 100;
des.at<uchar>(r, c) = gray;
}
}
}

/////////////改变图像的对比度和亮度/////////////////////////////////////
///@para a float 对比度 1.0~3.0
///@para b int 亮度 0~100
void ChangeGain(Mat &src, Mat &des, float a, int b)
{
//g(r,c) = a*f(r,c) + b
des.create(src.rows, src.cols, 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);
}
}
}
}

// 改变图像的尺寸
void xresize(Mat &src, Mat &des, Size size)
{
des.create(size, src.type());
//映射的原图坐标
int sx, sy = 0;
float fx = (float)src.cols / des.cols;
float fy = (float)src.rows / des.rows;
for (int x = 0; x < des.cols; x++)
{
sx = fx * x + 0.5;
for (int y = 0; y <des.rows; y++)
{
sy = fy * y + 0.5;
des.at<Vec3b>(y, x) = src.at<Vec3b>(sy, sx);
}
}

}

int main(int argc, char *argv[])
{
Mat src = imread("1.png");
src.create(3000, 4000, CV_8UC3);
Mat gray;
PrintMs("");
cvtColor(src, gray, COLOR_BGR2GRAY);
PrintMs("cvtColor1");

cvtColor(src, gray, COLOR_BGR2GRAY);
PrintMs("cvtColor2");
Mat mygray;
RGBToGray(src, mygray);
PrintMs("RGBToGray");

namedWindow("src");
namedWindow("gray");
namedWindow("mygray");

imshow("src", src);
imshow("gray", gray);
imshow("mygray", mygray);

waitKey(0);

return 0;
}