const app = getApp()

Page({
  data: {},

  onLoad: function () {

    // 通过 SelectorQuery 获取 Canvas 节点
    wx.createSelectorQuery()
      .select('#canvas')
      .fields({
        node: true,
        size: true,
      })
      .exec(this.init.bind(this))
  },

  init(res) {
    const ctx = canvas.getContext('2d')
    this.drawCar(ctx)
    const img = canvas.createImage()
    img.onload = () => {
      this._img = img
    }
    img.src = './car.png'
  },

  drawCar(ctx) {
    ctx.drawImage(this._img, 0, 0, 100, 50)
    ctx.restore()
  }
})