title: Headers for PNG image output to make sure it gets cached at browser?
body: <p>I have images (PNG) that are generated dynamically and will be embedded in websites and forums. When an image gets posted on a very busy page, there are a lot many connections to service for something that doesn't change often. I want to tell the browser for how long to cache it.</p>
  
  <p>So what headers do I need? Currently, I have:</p>
  
  <pre><code>Cache-Control: max-age=86400
  Content-Type: image/png
  </code></pre>
  
  <p>It seems that the browser is not caching the image (it is about 20-30kb). What else would be necessary?</p>
  
  <p>Edit:
  This is an example image, I already have an URL with <code>.png</code> extension:
  <a href="https://images.carspending.com/sigimg/5734/user/honda-accord-2-4i-executive-tourer_medium.png" rel="noreferrer">https://images.carspending.com/sigimg/5734/user/honda-accord-2-4i-executive-tourer_medium.png</a></p>