字體：

font-family:Monospaced Number,Chinese Quote,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,PingFang SC,Hiragino Sans GB,Microsoft YaHei,Helvetica Neue,Helvetica,Arial,sans-serif!important;

// 條形碼，二維碼

var barcode = require('./barcode');
function convert_length(length) {
    return Math.round(wx.getSystemInfoSync().windowWidth * length / 750);
}
function barc(id, code, width, height) {
    barcode.code128(wx.createCanvasContext(id), code, convert_length(width), convert_length(height))
}
var qrcode = require('./qrcode');
function qrc(id, code, width, height) {
    qrcode.api.draw(code, {
          ctx: wx.createCanvasContext(id),
          width: convert_length(width),
              height: convert_length(height),
              margin: 0
    })
}
module.exports = {
  barcode: barc,
  qrcode: qrc
}

// 單位rpx
barcode('id', code, 500, 200); 
qrcode('id', code, 200, 200);