uniapp如何将图片转base64

            urlTobase64(url){                // #ifdef MP-WEIXIN                    uni.getFileSystemManager().readFile({                        filePath: url, //选择图片返回的相对路径                        encoding: 'base64', //编码格式                        success: res => { //成功的回调                        console.log(res);                            let base64 = 'data:image/jpeg;base64,' + res.data //不加上这串字符，在页面无法显示的哦                        },fail: (e) => {                            console.log("图片转换失败");                        }                    })                // #endif                                // #ifndef MP-WEIXIN                    uni.request({                        url: url,                        method:'GET',                        responseType:'arraybuffer',                        success: ress => {                            let base64 = wx.arrayBufferToBase64(ress.data); //把arraybuffer转成base64                             base64 = 'data:image/jpeg;base64,' + base64 //不加上这串字符，在页面无法显示的哦                        },fail: (e) => {                            console.log("图片转换失败");                        }                    })                // #endif            }