這個剛開始不知道怎麼弄，後來問了下網友，原來一個spit函式搞定！

#include <cv.h>
#include <highgui.h>
//#include <math.h>

int main()
{

	IplImage* src = cvLoadImage( "F:\\hehua.jpg", 1 );
	IplImage * RedChannel = cvCreateImage( cvGetSize(src), 8, 1);
	IplImage * GreenChannel = cvCreateImage( cvGetSize(src), 8, 1);
	IplImage * BlueChannel = cvCreateImage( cvGetSize(src), 8, 1);
	IplImage * alphaChannel = cvCreateImage( cvGetSize(src), 8, 1);
	cvSplit(src,BlueChannel,GreenChannel,RedChannel,0);

	cvNamedWindow( "RedChannel", 1 );
	cvNamedWindow( "GreenChannel", 1 );
	cvNamedWindow( "BlueChannel", 1 );
	cvNamedWindow( "lphaChannel", 1 );

	cvShowImage( "RedChannel", RedChannel );
	cvShowImage( "GreenChannel", GreenChannel );
	cvShowImage( "BlueChannel", BlueChannel );
	cvShowImage( "lphaChannel", alphaChannel );

	cvWaitKey(0);
	cvReleaseImage( &RedChannel );
	cvReleaseImage( &GreenChannel );
	cvReleaseImage( & BlueChannel );
	cvReleaseImage( & alphaChannel );

	return 0;
}
 

cvSplit(src,BlueChannel,GreenChannel,RedChannel,0);