title: Metric for binary segmentation network
body: <p>I am working on segmentation with 2 classes (object and background), and I have 2 types of unbalance:
  1. inside the image - the object of interest is small with respect to the background
  2. about 80% of my images are only background.</p>
  
  <p>I want to know which metrics are good for this situation.</p>
  
  <p>I think that using F1 on each image and then averaging (like keras does) is wrong because the images without any objects will change the results drastically (for example, if I have only one pixel which is FP on empty image, I get F-score of zero while its very good segmentation). </p>
  
  <p>What is the right way to test the performance of my network?</p>
  
  <p>thank you all</p>