MAC上安装node-canvas

安装Node.js的canvas库时发现canvas依赖cairo包：

$ npm install canvas...> node-gyp rebuild...No package 'cairo' found

可以通过brew安装，但是安装时发现cairo依赖于X11：

$ brew install cairocairo: Unsatisfied dependency: XQuartz Homebrew does not package XQuartz. Installers may be found at:

x11可以从官网https://xquartz.macosforge.org下载，安装即可。

安装完要设置环境变量不然会报如下错误：

$ npm install canvas...Package xcb-shm was not found in the pkg-config search path.Perhaps you should add the directory containing `xcb-shm.pc'to the PKG_CONFIG_PATH environment variablePackage 'xcb-shm', required by 'cairo', not found

环境变量的设置：

$ export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig:/opt/X11/lib/pkgconfig

然后依次安装就可以了：

$ brew install cairo

$ npm install canvas