wxml代码：

<ec-canvas id="mychart-dom-pie" canvas-id="mychart-pie" ec="{{ ecPie }}"></ec-canvas>

js代码：

var pieId = this.selectComponent('#mychart-pie');

pieId.canvasToTempFilePath({

x: 100,

  y: 200,

  width: 50,

  height: 50,

  destWidth: 100,

  destHeight: 100,

  fileTpye:'png',

  canvasId: 'mychart-pie',

  success(res) {

console.log(res.tempFilePath);

imgUrl=res.tempFilePath;

wx.saveImageToPhotosAlbum({

filePath:res.tempFilePath

})

  },

  fail(error){

console.log(error);  

  }

   },this);

没有报错，保存的图片打开后空白