使用 new FileReader 将图片文件流转化成base6

// blob = 文件流
 const blobToDataURL = (blob) => {
        return new Promise((resolve, reject) => {
            let reader = new FileReader();
            reader.addEventListener('load', () => {
                resolve(reader.result); // reader.result即为包含文件内容的字符串
            });
            reader.readAsDataURL(blob);
        });
    };

返回base64编码

data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQH/2wBDAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQH/wAARCBOyBDgDASIAAhEBAxEB/8QAHwAAAQQDAQEBAQAAAAAAAAAAAAUGBwgDBAkCAQoL/8QAhBAAAQMCBAMFBQUGAwUBAAFFAQIDEQQhAAUSMQZBUQcTImFxFDKBkaEII7HB8AkVQtHh8RYzUgoXGCRictMlQ1aCphkaJig0NjhFU4WS1zVGVViiqLLExSc3REhjZGhzhJSVl7PC0kd1eIaIk9QpV....