title: Can a PNG image contain multiple pages?
body: <p>On OSX I converted a multi-page PDF file to PNG and (somehow) it created a multi-page PNG file.</p>
  
  <p><a href="https://i.stack.imgur.com/3LLYk.png" rel="noreferrer"><img src="https://i.stack.imgur.com/3LLYk.png" alt="enter image description here"></a></p>
  
  <p>Is there an extension to the PNG format that allows this? Or is this not something I can validly create?</p>
  
  <p>~~~~</p>
  
  <p>To clarify, this is a PNG file, per the builtin <code>file</code> command and the <code>identify</code> command from imagemagick.</p>
  
  <pre><code>$ file algorithms-combined-print.png 
  algorithms-combined-print.png: PNG image data, 1275 x 1650, 8-bit/color RGBA, non-interlaced
  
  $ identify algorithms-combined-print.png 
  algorithms-combined-print.png PNG 1275x1650 1275x1650+0+0 8-bit sRGB 3.537MB 0.000u 0:00.000
  </code></pre>
  
  <p>And here is a pastebin of the command <code>identify -verbose algorithms-combined-print.png</code>: <a href="http://pastebin.com/hw1yuRKa" rel="noreferrer">http://pastebin.com/hw1yuRKa</a></p>
  
  <p>What is notable from that output is that the pixel count is <code>Number pixels: 2.104M</code> which corresponds to one page. However, the file size is 3.537MB, which is clearly sufficient to hold all the pages.</p>
  
  <p>Per request, here is the output of <code>pngcheck</code>: <a href="http://pastebin.com/aCRMEd9L" rel="noreferrer">http://pastebin.com/aCRMEd9L</a></p>