将2个三通道的图片，合成新的一个三通道图片

 Mat[] afMat =  Cv2.Split(new Mat(grrenFilePath));
 Mat[] shgMat = Cv2.Split(new Mat(redFilePath));
 Mat blueMat = new Mat(new OpenCvSharp.Size(512, 512), OpenCvSharp.MatType.CV_8UC1);
 blueMat.SetTo(0);
 Mat resultMat = new Mat(new OpenCvSharp.Size(512, 512), OpenCvSharp.MatType.CV_8UC3);
 Cv2.Merge(new Mat[] { blueMat, afMat[1], shgMat[2] }, resultMat);
 resultMat.SaveImage(mergeaPath);

其中，

2个三通道，一个是绿色伪彩图片，文件路径是 grrenFilePath，

一个是红色伪彩图片，文件路径是 redFilePath，

新的三通道，即为2个三通道的合并，文件路径是 mergeaPath