title: How to count the number of particles of a certain size in an image?
body: <p>Is there a good algorithm for detecting particles based on size? For example, I have the following image, and I want to detect and count particles that are highlighted in the below image:
  <a href="https://i.stack.imgur.com/wE17z.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wE17z.png" alt="enter image description here"></a></p>
  
  <p><a href="https://i.stack.imgur.com/JNKtp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/JNKtp.png" alt="enter image description here"></a></p>
  
  <p>It's basically based on size. The third circle from the left is about 20 microns and I want to count all the particles that meet that threshold.</p>
  
  <p>How can I go about doing this? I need to do this for 10,000 images?</p>
  
  <p>Thanks</p>