如何使用 falcon 服务器流式传输视频（运动 jpeg）？

Question

期望的输出

输入：使用 OpenCV 或来自 REST 摄像头 URL 的摄像头馈送。 （不关心这个问题）

输出：在进行一些 OpenCV 处理后流式传输 jpeg 图像

---

到目前为止，我已经根据Falcontutorial做了以下工作

输入：图像文件作为 POST 请求

输出：带有图像路径的 GET 请求端点

import mimetypes
import os
import re
import uuid
import cv2
import io
import falcon
from falcon import media
import json
import msgpack

class Collection(object):

    def __init__(self, image_store):
        self._image_store = image_store

    def on_get(self, req, resp):
        # TODO: Modify this to return a list of href's based on
        # what images are actually available.
        doc = {
            'images': [
                {
                    'href': '/images/1eaf6ef1-7f2d-4ecc-a8d5-6e8adba7cc0e.png'
                }
            ]
        }

        resp.data = msgpack.packb(doc, use_bin_type=True)
        resp.content_type = falcon.MEDIA_MSGPACK
        resp.status = falcon.HTTP_200

    def on_post(self, req, resp):
        name = self._image_store.save(req.stream, req.content_type)
        # Unnecessary Hack to read the saved file in OpenCV
        image = cv2.imread("images/" + name)
        new_image = do_something_with_image(image)
        _ = cv2.imwrite("images/" + name, new_image)
        resp.status = falcon.HTTP_201
        resp.location = '/images/' + name


class Item(object):

    def __init__(self, image_store):
        self._image_store = image_store

    def on_get(self, req, resp, name):
        resp.content_type = mimetypes.guess_type(name)[0]
        resp.stream, resp.stream_len = self._image_store.open(name)


class ImageStore(object):

    _CHUNK_SIZE_BYTES = 4096
    _IMAGE_NAME_PATTERN = re.compile(
        '[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}\.[a-z]{2,4}$'
    )

    def __init__(self, storage_path, uuidgen=uuid.uuid4, fopen=io.open):
        self._storage_path = storage_path
        self._uuidgen = uuidgen
        self._fopen = fopen

    def save(self, image_stream, image_content_type):
        ext = mimetypes.guess_extension(image_content_type) # Issue with this code, Not returning the extension so hard coding it in next line
        ext = ".jpg"
        name = '{uuid}{ext}'.format(uuid=self._uuidgen(), ext=ext)
        image_path = os.path.join(self._storage_path, name)

        with self._fopen(image_path, 'wb') as image_file:
            while True:
                chunk = image_stream.read(self._CHUNK_SIZE_BYTES)
                if not chunk:
                    break

                image_file.write(chunk)

        return name

    def open(self, name):
        # Always validate untrusted input!
        if not self._IMAGE_NAME_PATTERN.match(name):
            raise IOError('File not found')

        image_path = os.path.join(self._storage_path, name)
        stream = self._fopen(image_path, 'rb')
        stream_len = os.path.getsize(image_path)
        return stream, stream_len


def create_app(image_store):
    api = falcon.API()
    api.add_route('/images', Collection(image_store))
    api.add_route('/images/{name}', Item(image_store))
    api.add_sink(handle_404, '')
    return api


def get_app():
    storage_path = os.environ.get('LOOK_STORAGE_PATH', './images')
    image_store = ImageStore(storage_path)
    return create_app(image_store)

响应是这样的：

HTTP/1.1 201 创建

连接：关闭

日期：格林威治标准时间 2018 年 12 月 3 日星期一 13:08:14

服务器：gunicorn/19.7.1

内容长度：0

内容类型：应用程序/json； charset=UTF-8

位置：/images/e69a83ee-b369-47c3-8b1c-60ab7bf875ec.jpg

上面的代码有2个问题：

1. 我首先获取数据流并将其保存在一个文件中，然后在 OpenCV 中读取它以执行一些其他操作，这些操作相当矫枉过正，应该很容易修复，但我不知道如何
2. 此服务不流式传输 JPG。我只有一个 GET 请求 url，我可以在浏览器中打开它来查看不理想的图像

那么，如何将 req.stream 数据读取为 numpy 数组？更重要的是，我需要进行哪些更改才能从该服务流式传输图像？

附：抱歉发了这么长的帖子

Answer 1

我找到了一个完美的解决方案。欲了解更多信息，请查看this beautiful code。

def gen(camera):
    while True:
        image = camera.get_frame()
        new_image = do_something_with_image(image)
        ret, jpeg = cv2.imencode('.jpg', new_image)
        yield (b'--frame\r\n'
               b'Content-Type: image/jpeg\r\n\r\n' + jpeg.tobytes() + b'\r\n\r\n')


class StreamResource(object):
    def on_get(self, req, resp):
        labeled_frame = gen(VideoCamera())
        resp.content_type = 'multipart/x-mixed-replace; boundary=frame'
        resp.stream = labeled_frame

def get_app():
    api = falcon.API()
    api.add_route('/feed', StreamResource())
    return api