could not load library GraphocsMagickWand:tutorials/coursera_neural_nets/assignment1

[anjiang2016]

error info::
/torch/install/share/lua/5.2/graphicsmagick/Image.lua:322: could not load library GraphicsMagickWand
stack traceback:
[C]: in function 'error'
/home/anjiang/torch/install/share/lua/5.2/trepl/init.lua:386: in function 'require'
main.lua:5: in main chunk
[C]: in function 'dofile'
...iang/torch/install/lib/luarocks/rocks/trepl/scm-1/bin/th:145: in main chunk
[C]: in ?

[anjiang2016]

I try to change /torch/install/share/lua/5.2/graphicsmagick/Image.lua:322 like this:
local clib = ffi.load('GraphicsMagickWand')
==>
local clib = ffi.load('MagickWand')
and,then,it works