微信小程序pc版使用canvas.createImage()不走onload和onerror回调
const canvas = res[0].node;
          const ctx = canvas.getContext('2d');
          let frontImg = canvas.createImage()
          frontImg.src = item.src;
          frontImg.onload = (res) => {
            console.log(res)
          })
          frontImg.onload = (err) => {
            console.log(err)
          })

https://developers.weixin.qq.com/s/C1F1v4mC7JM7 代码片段