QT显示调用C++编译的dll

//定义函数指针：
typedef cv::Mat(*Fun)(std::string); //定义函数指针，以备调用  
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void  ImageMaster_Pro::Img_stich()
{
	QString imgpath = QFileDialog::getExistingDirectory(this, "待拼接影像文件夹", "./", QFileDialog::ShowDirsOnly);
	QLibrary mylib("ImgStiching_dll.dll");   //声明所用到的dll文件  
	if (imgpath.isEmpty())
	{
		return;
	}
	else
	{
		cv::Mat result;
		if (mylib.load())              //判断是否正确加载  
		{
			Fun open = (Fun)mylib.resolve("ImgStich");    //援引 add() 函数  
			if (open)                  //是否成功连接上 add() 函数  
			{
				result = open(imgpath.toStdString());
				QImage outimg;
				QString savepath = "1.jpg";
				cv::imwrite(savepath.toStdString(), result);
				outimg.load(savepath);
				ShowImage(outimg, true);
			}
			else
				QMessageBox::information(NULL, "NO", "Linke to Function is not OK!!!!");
		}
	}
}