title: How to annotate the ground truth for image segmentation?
body: <p>I'm trying to train a CNN model that perform image segmentation,
  but I'm confused how to create the ground truth if I have several
  image samples?</p>
  
  <p>Image segmentation can classify each pixel in input image to 
  a pre-defined class, such as cars, buildings, people, or any else.</p>
  
  <p>Is there any tools or some good idea to create the ground
  truth for image segmentation?</p>
  
  <p>Thanks!</p>