背景：
1 使用了nodejs 版本的gm：https://github.com/aheckmann/gm
2 系统：centos7
3 报错：
Could not execute GraphicsMagick/ImageMagick: gm "identify" "-ping" "-format" "%wx%h" "/mnt/data/static/tmp/upload_54ac1f78f289e1361ebf1263c4fcf9e1" this most likely means the gm/convert binaries can't be found
解决方案：
centos 需要安装graphicimage，参考：https://gist.github.com/abernardobr/e4292953fc84f9456cfa
| |
> wget ftp://ftp.graphicsmagick.org/pub/GraphicsMagick/GraphicsMagick-LATEST.tar.gz |
| > tar -xzvf GraphicsMagick-LATEST.tar.gz | |
| > cd GraphicsMagick-1.3.21 (or the lastest graphics magick) | |
| # Install Graphics Magick | |
| ## Get libs | |
| > yum install libpng libjpeg libpng-devel libjpeg-devel ghostscript libtiff libtiff-devel freetype freetype-devel jasper jasper-devel | |
| ## Install GM with OpenMP | |
| > ./configure | |
| > make install | |
| > gm version |
