Can't install RMagick 2.13.1. Can't find MagickWand.h.
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ln -s /usr/local/include/ImageMagick/wand /usr/local/include/wand
ln -s /usr/local/include/ImageMagick/magick /usr/local/include/magick
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/usr/local/include/ImageMagick为ImageMagick安装目录
This installation of RMagick was configured with ImageMagick 6.7.5 but ImageMagick 6.5.7-8 is in use.
提示使用版本和配置版本不同时，在rmagick.rb首行添加
RMAGICK_BYPASS_VERSION_TEST = true
