uniapp-vue2-微信小程序，canvas 裁切图片的代码

<canvas class="edit-question-canvas" type="2d" id="canvasCuteImage"></canvas>
 
/*
.edit-question-canvas {
      position: absolute;
      left: -750rpx;
      width: 690rpx;
      height: 100rpx;
    }
样式随便自己写
 
*/
 
// 使用方法
let path = await this.canvasCuteImageExecute(item.data.path, 690, item.data.rect, '#canvasCuteImage', this.pxRatio)
 
/*
path：本地图片的地址
w: 截取后图片的宽度
rect:[x,y,width,height] 解决的矩形范围
canvasId:canvas id
pxRatio：rpx 转 px 的比例
onLoad() {
      let that = this
      uni.getSystemInfo({
        success: function(res) {
          that.pxRatio = res.windowWidth / 750
        }
      })
    },
          
 
*/
canvasCuteImageExecute(path, w, rect, canvasId, pxRatio) {
        return new Promise((resolve, reject) => {
          let canvasHeight = Math.floor(w * rect[3] / rect[2])
          let x = rect[0]
          let y = rect[1]
          let width = rect[2]
          let height = rect[3]
          let destWidth = w * pxRatio
          let destHeight = canvasHeight * pxRatio
 
          const query = wx.createSelectorQuery()
          query.select(canvasId)
            .fields({
              node: true,
              size: true
            })
            .exec((res) => {
              const canvas = res[0].node
              const ctx = canvas.getContext('2d')
              canvas.width = destWidth
              canvas.height = destHeight
              let image = canvas.createImage(); //创建image实例
              image.src = path
              image.onload = function() {
                ctx.drawImage(image, x, y, width, height, 0, 0, destWidth, destHeight);
                wx.canvasToTempFilePath({
                  canvas: canvas,
                  success(res) {
                    // console.log(res.tempFilePath);
                    resolve(res.tempFilePath)
                  },
                  fail(err) {
                    console.log(err)
                    resolve('')
                  }
                })
              }
            })
 
        })
        // 计算 canvas 的高度
      },