split函数的主要功能是把一个彩色图像分割成3个通道，方便进一步的图像处理，具体说明如下：

split Divides a multi-channel array into several single-channel arrays.
C++: void split(const Mat& mtx, Mat* mv)
C++: void split(const Mat& mtx, vector& mv)

其实还有一个函数merge可以实现相反的操作，简单说明如下：

merge Composes a multi-channel array from several single-channel arrays.
C++: void merge(const Mat* mv, size_t count, OutputArray dst)
C++: void merge(const vector& mv, OutputArray dst)

其示例代码如下：

#include "stdafx.h"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"

using namespace cv;
int main( int argc, char** argv )
{

   Mat src, srcOfMerge;
   vector mv;
   /// Read image ( same size, same type )
   src = http://www.mamicode.com/imread("d:\\images\\WindowsLogo.jpg");
   if( !src.data ) { printf("Error loading src \n"); return -1; }
   split(src,mv);
   /// Create Windows
   namedWindow("RGB", 1);
   namedWindow("R", 1);
   namedWindow("R", 1);
   namedWindow("R", 1);
   namedWindow("srcOfMerge", 1);
   imshow( "RGB", src);
   imshow("R",mv[0]);
   imshow("G",mv[1]);
   imshow("B",mv[2]);
   merge(mv,srcOfMerge);
   imshow("srcOfMerge",srcOfMerge);
   waitKey(0);
   return 0;
}

split函数和merge函数