苹果手机微信升级到8.0.27，微信小程序压缩绘图异常，一直循环压缩。8.0.26正常

function getCanvasImage(canvasId, imagePath, imageW, imageH, getImgsuccess) {

  const ctx = wx.createCanvasContext(canvasId);

  ctx.drawImage(imagePath, 0, 0, imageW, imageH);

  ctx.draw(false, () => {

    wx.canvasToTempFilePath({

      canvasId: canvasId,

      x: 0,

      y: 0,

      width: imageW,

      height: imageH,

      quality: 1,

      success(res) {

        getImgsuccess(res.tempFilePath);

      }

    });

  });