There are basically two schemes for making verification code under node.js: node CCAP and canvas. Installation is not easy. Installing vs C + + under windows, so give up and move to Ubuntu. Search for a long time. The following methods are simple and feasible.
sudo apt-get install libcairo2-dev libjpeg8-dev libpango1.0-dev libgif-dev build-essential g++ -y npm install -g canvas