Adding polygon to image without hold on

Hello, I am writing a program which detects logo in a video sequence. In this project I send a video sequence to the Matlab, it converts that sequence into frames, changes them to grayscale using rgb2gray function and detects logo on frame. Now i want to draw a polygon "around" this logo. Common solution is to plot image, use hold on and draw a line with a line function, but I want to do this without plotting each frame. Is there a way to do it? P.S. I'm sorry if my english is bad (I'm not a native speaker).