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