api去除背景后的图片用opencv读取显示后和原图一样

做背景去除，自己的抠图一直不理想，于是想到用网上的api抠图，但是去除背景后的图片用cv2显示出来和原图是一样的，不知道怎么解决。
代码如下：

import requests, os
import json
import hashlib, base64, hmac
import sys
info = sys.version_info
if info[0] < 3:
    is_python3 = False
else:
    is_python3 = True
app_key = '204056920'
secret = '2APXsC7mz4GEEtVJu3FD4s0W7YfE4TWH'
file_name = './1.jpg'
import cv2
import numpy
cv2.imshow('img',cv2.imread(file_name))
cv2.waitKey(0)
stage = 'RELEASE' # 正式环境
#stage = 'TEST' # 测试环境
# 普通物品扣图接口
def params_of_object_matting(photo_base64):
    print ('测试普通物品扣图接口 ...')
    host = 'https://objseg.market.alicloudapi.com'
    uri = '/commonseg/rgba'
    return host, uri, {
        'photo': photo_base64
    }
def test_segment():
    with open(file_name,'rb') as fp:
        photo_base64 = base64.b64encode(fp.read())
    if is_python3:
        photo_base64 = photo_base64.decode('utf8')

    _, photo_type = os.path.splitext(file_name)
    photo_type = photo_type.lstrip('.')

    # host, uri, body_json = params_of_portrait_matting(photo_base64, photo_type)
    host, uri, body_json = params_of_object_matting(photo_base64)
    # host, uri, body_json = params_of_idphoto(photo_base64, photo_type)
    # host, uri, body_json = params_of_head(photo_base64, photo_type)
    # host, uri,  body_json = params_of_crop(photo_base64)
    api = host + uri

    body = json.dumps(body_json)
    md5lib = hashlib.md5()
    if is_python3:
        md5lib.update(body.encode('utf8'))
    else:
        md5lib.update(body)
    body_md5 = md5lib.digest()
    body_md5 = base64.b64encode(body_md5)
    if is_python3:
        body_md5 = body_md5.decode('utf8')

    method = 'POST'
    accept = 'application/json'
    content_type = 'application/octet-stream; charset=utf-8'
    date_str = ''
    headers = ''

    string_to_sign = method + '\n' \
                    + accept + '\n' \
                    + body_md5 + '\n' \
                    + content_type + '\n' \
                    + date_str + '\n' \
                    + headers \
                    + uri
    if is_python3:
        signed = hmac.new(secret.encode('utf8'),
                          string_to_sign.encode('utf8'),
                          digestmod=hashlib.sha256).digest()
    else:
        signed = hmac.new(secret, string_to_sign, digestmod=hashlib.sha256).digest()
    signed = base64.b64encode(signed)
    if is_python3:
        signed = signed.decode('utf8')

    headers = {
        'Accept': accept,
        'Content-MD5': body_md5,
        'Content-Type': content_type,
        'X-Ca-Key': app_key,
        'X-Ca-Stage': stage,
        'X-Ca-Signature': signed
    }


    resp = requests.post(api, data=body, headers=headers)
    try:
        global res
        res = resp.content
        res = json.loads(res)
        #print ('res:', res)
        if str(res['status']) == '0':
            print ('成功!')
        else:
            print ('失败!')
    except:
        print('failed parse:', resp)


if __name__ == "__main__":
    test_segment()
    img_src = res['data']['result']
    import os,base64
    import requests as req
    from PIL import Image
    from io import BytesIO

    response = req.get(img_src)

    # 内存中打开图片
    image = Image.open(BytesIO(response.content))

    # 图片的base64编码
    ls_f = base64.b64encode(BytesIO(response.content).read())

    # base64编码解码
    imgdata = base64.b64decode(ls_f)

    # 图片文件保存
    file = open('test.png','wb')
    file.write(imgdata)
    file.close()
    cv2.imshow('img',cv2.imread('./test.png'))

这是原图

这是去除背景后的图

这是运行结果的截图

一开始以为是imread()函数少读了一个通道，后来发现都是jpg格式，不存在alpha通道问题

请问怎样才能把去除背景的图用cv2读出来？

把16行的#cv2.waitKey(0) 注释掉，这句话会让代码一直停留在此处无法向下运行。运行结果保存在当前文件夹下.png