sudo gem install rmagick Not working

I am installing rmagick,Its giving me error of

Found partial installation at: /usr checking for ImageMagick version >= 6.4.9... no Can't install RMagick开发者_如何转开发 2.13.1. You must have ImageMagick 6.4.9 or later.

Although I have installed the ImageMagick 6.5.7-8 ,Location is /usr/local/bin/identify,

I don't understand the what is the reason behind this.Please help me...

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I was just bitten by the same thing on Ubuntu 10.04. The fix was to install libmagick9-dev, not libmagick-dev (without the 9)