uniCloud.uploadFile如何上传base64编码后的文件

async updateUserInfo(openid, newInfo) {  
        const {  
            nickname,  
            avatar  
        } = newInfo  

        const regex = /[^\.]\w*$/  
        const imageType = avatar.match(regex)[0]  
        const base64Data = avatar.replace(/^data:image\/\w+;base64,/, "")  
        let bf = Buffer.from(base64Data, 'base64')  

        const checkMessageResult = await msgSecCheck(openid, nickname)  
        const checkImgResult = await imgSecCheck(bf)  
        if (checkMessageResult.result.suggest === "pass" && checkImgResult.errcode === 0) {  
            let result = await uniCloud.uploadFile({  
                cloudPath: `${base64Data.slice(0,8)}.${imageType}`,  
                fileContent: bf  
            })  
        }  
    }

将bf提交报错

请问base64编码后的图片要怎么转化成buffer对象传入呀