上传的图片已损坏，但未损坏txt文件

如何解决上传的图片已损坏，但未损坏txt文件

我正在尝试使用AWS lambdas上传图像，但是图像损坏了，我使用txt文件进行了测试，效果很好。函数checkImage是处理程序

def parse_into_field_storage(fp,ctype,clength):
    fs = FieldStorage(
        fp=fp,environ={'REQUEST_METHOD': 'POST'},headers={
            'content-type': ctype,'content-length': clength
        },keep_blank_values=True
    )
    form = {}
    files = {}
    for f in fs.list:
        if f.filename:
            files.setdefault(f.name,[]).append(f)
        else:
            form.setdefault(f.name,[]).append(f.value)
    return form,files
  
def checkImage(event,context):
    body_file = BytesIO(bytes(event["body"],"utf-8"))
    form,files = parse_into_field_storage(
        body_file,event['headers']['Content-Type'],body_file.getbuffer().nbytes
    )

    fileitem = files['file'][0]

    print(fileitem.filename)

    # Test if the file was uploaded
    if fileitem.filename:
        fn = os.path.basename(fileitem.filename)
        open('/tmp/' + fn,'wb').write(fileitem.file.read())
        message = 'The file "' + fn + '" was uploaded successfully'
    else:
        message = 'No file was uploaded'
    
    return {
        "statusCode": 200,"body": message
    }

当我从python打印文件时，我得到了

我使用了diff，二进制文件不同。我认为图像文件被解析成两倍或类似的东西 我猜这里我做错了什么

body_file = BytesIO(bytes(event["body"],"utf-8"))

我尝试了不同的形式，例如

fp = io.BytesIO(event['body'].encode('utf-8'))

但基本相同。