title: Insert a text chunk into a png image
body: <p>I'm looking for a simple command-line tool (on Linux) to insert a text chunk (e.g. copyright) into a png file, resulting in a new png file:</p>
  
  <pre><code>&gt; png-insert-text-chunk "here's my text chunk" &lt; in.png &gt; out.png
  </code></pre>
  
  <p>Note: by "insert a text chunk", I do not mean "draw some text on the image".  I mean: insert the text into the png file as a chunk, in the <a href="http://www.libpng.org/pub/png/spec/1.2/PNG-Encoders.html#E.Text-chunk-processing" rel="noreferrer">technical sense</a>.  This can be used, for example, to insert a copyright message that isn't displayed on the actual image.</p>