Update README.md

README.md

@@ -15,7 +15,7 @@ How to build it
 To compile this code, you would need:
 
 - cmake
-- graphicsmagick for 2D transforms
+- Imagemagick for 2D transforms
 - libvol/liblongvol for 3D transforms (https://liris.cnrs.fr/david.coeurjolly/code/simplevol.html) to be able to load ".vol" objects