使用canvas2d的方法，安卓手机vivo z5x 红米note8 pro等用canvasToTempFilePath生成图片提示canvasToTempFilePath:fail:convert native buffer parameter fail. native buffer exceed size limit，初步怀疑是宽度设置太大原因，设置了180vw。 <canvas id="canvas" canvas-id="signCanvas" type="2d" binderror="drawError" bindtouchstart="drawStart"  bindtouchmove="drawMove" bindtouchend="drawEnd"  style="width:{{width}}vw;height:100%;border:1px solid #ddd;margin:auto;margin-left:{{marginLeft}}vw;"> </canvas>   data: {     marginLeft: 0,     width: 180,     demoSrc: '',     title: '',     isShowCanvas: true,     // 默认一开始只有一个页面      isOnlyOnePage: true   },     init(res) {       console.log(res)       const width = res[0].width       const height = res[0].height       const canvas = res[0].node       console.log('初始化宽高度', width, height)       canvasWidth = width;       canvasHeight = height       signCanvas = canvas.getContext('2d')       canvas.width = width * dpr       canvas.height = height * dpr       canvasObj = canvas       signCanvas.scale(dpr, dpr)       signCanvas.lineWidth = 8;       signCanvas.lineCap = "round";       signCanvas.strokeStyle = "#222222";     },     // 保存确定     saveSign() {       let that = this;       let canHeight = 90;       let canWidth = this.data.width;       if (handData.length) {         console.log('canvas宽高', canvasWidth, canvasHeight)         console.log('dest图片宽度高度', canWidth, canHeight)         wx.canvasToTempFilePath({           x: 0,           y: 0,           destHeight: canHeight,           destWidth: canWidth,           canvas: canvasObj,           success: function (res) {             console.log('res', res)             that.setData({               demoSrc: res.tempFilePath             })             wx.downloadFile({               url: res.tempFilePath,               success: (res) => {                 console.log(res)               },               fail: (err) => {                 console.log(err)               }             })           },           fail: function (err) {             console.log('生成图片失败', err)             if (err && err.errMsg.indexOf('native buffer exceed size limit') >= 0) {               util.showModel('生成图片失败', '生成图片过大，请重新进入该页面，减少签名文字大小，降低右移次数')             } else if (err && err.errMsg) {               util.showModel('生成图片失败', err.errMsg)             } else {               util.showModel('生成图片失败', '请重新打开页面签名')             }           }         })       }     }

- 需求的场景描述（希望解决的问题） 越用越卡 - 希望提供的能力 清理缓存接口    能够   清理图片缓存