To convert a matix to vector in opencv

Question

I have written a code for creating a matrix which describes the features in a video.I use ROI for cropping the feature in images and saved it in a matrix.The whole program is inside a for loop.Now how to plot these matrix using imshow..

Mat patch;
for(unsigned int i=0;i<boundRect.size();i++)
{
Point centre=Point(boundRect[i].x+(boundRect[i].width)/2,boundRect[i].y+ (boundRect[i].height)/2);
circle(output,centre,5,CV_RGB(0,255,0),-1);
cv::Rect myROI(centre.x-40,centre.y+40,centre.x+40,centre.y-40);
patch=output(myROI);
}