title: Imagemagick -canny : what do arguments refer to?
body: <p>When using the -canny option of the Imagemagick convert tool, what do these arguments refer to ?</p>
  
  <p><code>-canny radiusxsigma{+lower-percent}{+upper-percent}</code></p>
  
  <p>The documentation (<a href="https://www.imagemagick.org/script/command-line-options.php#canny" rel="nofollow noreferrer">https://www.imagemagick.org/script/command-line-options.php#canny</a>) gives examples of what increase or decrease of percents may result in, but I can't find the exact meaning of radiusXsigma and its relation to the two numbers following (i.e. 10% and 30% in the doc example).</p>