diff --git a/how_to b/how_to
index a00f872..b29605d 100644
--- a/how_to
+++ b/how_to
@@ -475,4 +475,6 @@ Better Bibtex, Zotero:
             }
         }
 
-
+ImageMagick:
+    crop to aspect ratio
+        convert in.png -gravity center -crop 4:3 out.png