title: OpenCV: How to use HOGDescriptor::detect method?
body: <p>I have succeeded in tracking moving objects in a video.
  <img src="https://i.stack.imgur.com/FPL7G.jpg" alt="http://ww1.sinaimg.cn/mw690/63a9e398jw1ecn39e3togj20jv0g1gnv.jpg"></p>
  
  <p>However I want to decide if an object is person or not. I have tried the <code>HOGDescriptor</code> in OpenCV. HOGDescriptor have two methods for detecting people: <code>HOGDescriptor::detect</code>, and <code>HOGDescriptor::detectMultiScale</code>. OpenCV <em>"sources\samples\cpp\peopledetect.cpp"</em> demonstrates how to use <code>HOGDescriptor::detectMultiScale</code> , which search around the image at different scale and is very slow. </p>
  
  <p>In my case, I have tracked the objects in a rectangle. I think using <code>HOGDescriptor::detect</code> to detect the inside of the rectangle will be much more quickly. But the OpenCV document only  have the <code>gpu::HOGDescriptor::detect</code> (I still can't guess how to use it) and missed <code>HOGDescriptor::detect</code>. I want to use <code>HOGDescriptor::detect</code>.</p>
  
  <p>Could anyone provide me with some c++ code snippet demonstrating the usage of <code>HOGDescriptor::detect</code>?</p>
  
  <p>thanks.</p>