以前实现RGB图像转换成灰度图像都是直接调用OpenCV的库函数RGB2GRAY(IplImage* src);最近老板让我们除了读入输出图像实时用OpenCV的函数，其余的最好都是自己写，所以我自己上网查了一些资料，得到了一些转换算法，并且用c语言实现，具体归纳下来有如下三种：

方法一.对于RGB转灰度，有一个很著名的心理公式：Gray = r*0.299 + g*0.587 + b*0.114;

方法二.Adobephotoshop的公式：Adobe RGB(1998)[gamma = 2.20], gray = (r^2.2 * 0.2973 + g^2.2 * 0.6274 + b^2.2 * 0.0753)^(1/2.2);

方法三.平均值：gray = (r + b + r) / 3;

具体代码如下：

/*****************************************************************************************************

*File name: RGB2Gray.cpp

*Author: source code by RamiYim

*Version: cs-hhu-cn0.0

*Date: 2014.11.13

*Description: read a RGB frame, change it to Gray.

*Others:

*Function List: main functions and its function

*History: ,<20141113>,,

******************************************************************************************************/

#include "RGB2Gray.h"

#include "cv.h"

#include "highgui.h"

#include "math.h"

#include

void RGB2GrayTypical(int sizeOfPixel, char *imageData);

void RGB2GrayInPhotoShop(int sizeOfPixel, char *imageData);

void RGB2GrayAverage(int sizeOfPixel, char *imageData);

char *gray;//用于存放转换后的灰度像素值

void main(){

IplImage *srcImage = cvLoadImage("D:\\testdata\\lena.jpg");

cvShowImage("srcImage", srcImage);

int width = srcImage->width;//图像宽度

int height = srcImage->height;//图像高度

int nChannels = srcImage->nChannels;//通道数

int sizeOfPixel = width * height;//像素数

IplImage *grayImage = cvCreateImage(cvSize(width, height), IPL_DEPTH_8U, 1);//创建灰度图像

gray = (char *) malloc(sizeof(char) * width * height);//灰度图像的＂imageData＂初始化

RGB2GrayTypical(sizeOfPixel, srcImage->imageData);//转换成gray图像

grayImage->imageData = gray;

cvShowImage("grayImageTypical", grayImage);

RGB2GrayInPhotoShop(sizeOfPixel, srcImage->imageData);//转换成gray图像

grayImage->imageData = gray;

cvShowImage("RGB2GrayInPhotoShop", grayImage);

RGB2GrayAverage(sizeOfPixel, srcImage->imageData);

grayImage->imageData = gray;

cvShowImage("RGB2GrayAverage", grayImage);

cvWaitKey();

}

/******************************************************************************************************

*Function:RGB2GrayTypical()

*Description：输入一帧RGB图像，得到其灰度图像

*Calls://none

*Called by：//main

*Input：//none

*Output：//none

*Return://void

*Others：//算法思想：Gray = R*0.299 + G*0.587 + B*0.114

*History: ,<20141113>,,

******************************************************************************************************/

void RGB2GrayTypical(int sizeOfPixel, char *imageData){

for (int i = 0; i < sizeOfPixel; i++)

{

uchar b = (uchar)imageData[3 * i + 0];

uchar g = (uchar)imageData[3 * i + 1];

uchar r = (uchar)imageData[3 * i + 2];

gray[i] = r * 0.299 + g * 0.587 + b * 0.114;

}

}

/******************************************************************************************************

*Function:RGB2GrayInPhotoShop()

*Description：输入一帧RGB图像，得到其灰度图像

*Calls://none

*Called by：//main

*Input：//none

*Output：//none

*Return://void

*Others：//算法思想：Gray = (R^2.2 * 0.2973 + G^2.2 * 0.6274 + B^2.2 * 0.0753)^(1/2.2)

*History: ,<20141114>,,

******************************************************************************************************/

void RGB2GrayInPhotoShop(int sizeOfPixel, char *imageData){

for (int i = 0; i < sizeOfPixel; i++)

{

uchar b = imageData[3 * i + 0];

uchar g = imageData[3 * i + 1];

uchar r = imageData[3 * i + 2];

gray[i] = pow((pow(r, 2.2) * 0.2973 + pow(g, 2.2) * 0.6274 + pow(b, 2.2) * 0.0753), 1/2.2);

}

}

/******************************************************************************************************

*Function:RGB2GrayAverage()

*Description：输入一帧RGB图像，通过均值法得到其灰度图像

*Calls://none

*Called by：//main

*Input：//none

*Output：//none

*Return://void

*Others：//算法思想：gray = (r + g + b) / 3

*History: ,<20141114>,,

******************************************************************************************************/

void RGB2GrayAverage(int sizeOfPixel, char *imageData){

for (int i = 0; i < sizeOfPixel; i++)

{

uchar b = imageData[3 * i + 0];

uchar g = imageData[3 * i + 1];

uchar r = imageData[3 * i + 2];

gray[i] = (b + g + r) / 3;

}

}

输出结果如下：