我需要提供实时图形，我想通过http提供mjpeg流（以便使用普通标签轻松地将图形包含在网页中）。
是否可以从多个 jpeg 图像实时创建 mjpeg 流？
我的策略是：
-
输出正确的 http 标头：
Cache-Control:no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0 Connection:close Content-Type:multipart/x-mixed-replace;boundary=boundarydonotcross Expires:Mon, 3 Jan 2000 12:34:56 GMT Pragma:no-cache Server:MJPG-Streamer/0.2（从
curl -I {on a mjpeg-streamer instance}那里得到的，但这似乎很奇怪） -
只需生成连续的 jpeg 图像二进制文件，注意：
- 在
流的开头加上正确的标头（就像 MJPEG-streamer 所做的那样）：
Content-Type: image/jpeg Content-Length: 5427 X-Timestamp: 3927662.086099在每个 JPEG 流的末尾追加边界字符串。
--boudary--
问题：
你做到了吗，
你知道一个这样做的 Python 模块吗？
你认为它会起作用吗，
你有什么建议吗？
我让它作为概念验证：https://github.com/damiencorpataux/pymjpeg
对于内存：
import os, time
from glob import glob
import sys
from BaseHTTPServer import HTTPServer, BaseHTTPRequestHandler
boundary = '--boundarydonotcross'
def request_headers():
return {
'Cache-Control': 'no-store, no-cache, must-revalidate, pre-check=0, post-check=0, max-age=0',
'Connection': 'close',
'Content-Type': 'multipart/x-mixed-replace;boundary=%s' % boundary,
'Expires': 'Mon, 3 Jan 2000 12:34:56 GMT',
'Pragma': 'no-cache',
}
def image_headers(filename):
return {
'X-Timestamp': time.time(),
'Content-Length': os.path.getsize(filename),
#FIXME: mime-type must be set according file content
'Content-Type': 'image/jpeg',
}
# FIXME: should take a binary stream
def image(filename):
with open(filename, "rb") as f:
# for byte in f.read(1) while/if byte ?
byte = f.read(1)
while byte:
yield byte
# Next byte
byte = f.read(1)
# Basic HTTP server
class MyHandler(BaseHTTPRequestHandler):
def do_GET(self):
self.send_response(200)
# Response headers (multipart)
for k, v in pymjpeg.request_headers().items():
self.send_header(k, v)
# Multipart content
for filename in glob('img/*'):
# Part boundary string
self.end_headers()
self.wfile.write(pymjpeg.boundary)
self.end_headers()
# Part headers
for k, v in pymjpeg.image_headers(filename).items():
self.send_header(k, v)
self.end_headers()
# Part binary
for chunk in pymjpeg.image(filename):
self.wfile.write(chunk)
def log_message(self, format, *args):
return
httpd = HTTPServer(('', 8001), MyHandler)
httpd.serve_forever()
您可以使用 Flask 框架来执行此操作。
它不仅适用于 mjpeg。
我从这里改编了一些代码：https://blog.miguelgrinberg.com/post/video-streaming-with-flask
APP.py
#!/usr/bin/env python
from importlib import import_module
import os
from flask import Flask, render_template, Response
# import camera driver
if os.environ.get('CAMERA'):
Camera = import_module('camera_' + os.environ['CAMERA']).Camera
else:
from camera import Camera
# Raspberry Pi camera module (requires picamera package)
# from camera_pi import Camera
app = Flask(__name__)
@app.route('/')
def index():
"""Video streaming home page."""
return render_template('index.html')
def gen(camera):
"""Video streaming generator function."""
while True:
frame = camera.get_frame()
yield (b'--framern'
b'Content-Type: image/jpegrnrn' + frame + b'rn')
@app.route('/video_feed')
def video_feed():
"""Video streaming route. Put this in the src attribute of an img tag."""
return Response(gen(Camera()),
mimetype='multipart/x-mixed-replace; boundary=frame')
if __name__ == '__main__':
app.run(host='0.0.0.0', threaded=True)
base_camera.py
import time
import threading
try:
from greenlet import getcurrent as get_ident
except ImportError:
try:
from thread import get_ident
except ImportError:
from _thread import get_ident
class CameraEvent(object):
"""An Event-like class that signals all active clients when a new frame is
available.
"""
def __init__(self):
self.events = {}
def wait(self):
"""Invoked from each client's thread to wait for the next frame."""
ident = get_ident()
if ident not in self.events:
# this is a new client
# add an entry for it in the self.events dict
# each entry has two elements, a threading.Event() and a timestamp
self.events[ident] = [threading.Event(), time.time()]
return self.events[ident][0].wait()
def set(self):
"""Invoked by the camera thread when a new frame is available."""
now = time.time()
remove = None
for ident, event in self.events.items():
if not event[0].isSet():
# if this client's event is not set, then set it
# also update the last set timestamp to now
event[0].set()
event[1] = now
else:
# if the client's event is already set, it means the client
# did not process a previous frame
# if the event stays set for more than 5 seconds, then assume
# the client is gone and remove it
if now - event[1] > 5:
remove = ident
if remove:
del self.events[remove]
def clear(self):
"""Invoked from each client's thread after a frame was processed."""
self.events[get_ident()][0].clear()
class BaseCamera(object):
thread = None # background thread that reads frames from camera
frame = None # current frame is stored here by background thread
last_access = 0 # time of last client access to the camera
event = CameraEvent()
def __init__(self):
"""Start the background camera thread if it isn't running yet."""
if BaseCamera.thread is None:
BaseCamera.last_access = time.time()
# start background frame thread
BaseCamera.thread = threading.Thread(target=self._thread)
BaseCamera.thread.start()
# wait until frames are available
while self.get_frame() is None:
time.sleep(0)
def get_frame(self):
"""Return the current camera frame."""
BaseCamera.last_access = time.time()
# wait for a signal from the camera thread
BaseCamera.event.wait()
BaseCamera.event.clear()
return BaseCamera.frame
@staticmethod
def frames():
""""Generator that returns frames from the camera."""
raise RuntimeError('Must be implemented by subclasses.')
@classmethod
def _thread(cls):
"""Camera background thread."""
print('Starting camera thread.')
frames_iterator = cls.frames()
for frame in frames_iterator:
BaseCamera.frame = frame
BaseCamera.event.set() # send signal to clients
time.sleep(0)
# if there hasn't been any clients asking for frames in
# the last 10 seconds then stop the thread
if time.time() - BaseCamera.last_access > 10:
frames_iterator.close()
print('Stopping camera thread due to inactivity.')
break
BaseCamera.thread = None
camera.py
#D:gstreamer1.0x86bin>gst-launch-1.0.exe multifilesrc loop=true start-index=0 stop-index=0 location=d:/python/temp.png ! decodebin ! identity sleep-time=1000000 ! videoconvert ! autovideosink
import shutil
import time
import os,sys
from PIL import Image, ImageFont, ImageDraw, ImageFile
from io import BytesIO
from base_camera import BaseCamera
im = Image.new("RGB", (300, 30), (220, 180, 180))
#im.format'JPEG'
dr = ImageDraw.Draw(im)
font = ImageFont.truetype(os.path.join("fonts", "msyh.ttf"), 16)
text =time.strftime("%m/%d %H:%M:%S") +u"这是一段测试文本。"
dr.text((10, 5), text, font=font, fill="#000000")
im.save("d://python/temp.jpg")
dr.rectangle((0,0,300,500),fill="#FFFFFF")
text =time.strftime("%m/%d %H:%M:%S") +u"这是一段测试文本。"
dr.text((10, 5),text, font=font, fill="#000000")
f = BytesIO()
f.name="sdf.jpg"
im.save(f,"JPEG")
f.seek(0)
f.close()
class Camera(BaseCamera):
"""An emulated camera implementation that streams a repeated sequence of
files 1.jpg, 2.jpg and 3.jpg at a rate of one frame penr second."""
imgs = [open(f + '.jpg', 'rb').read() for f in ['1', '2', '3']]
@staticmethod
def frames():
while True:
text =time.strftime("%m/%d %H:%M:%S") +u"这是一段测试文本。"
dr.rectangle((0,0,300,500),fill="#FFFFFF")
dr.text((10, 5), text, font=font, fill="#000000")
f = BytesIO()
im.save(f,'JPEG')
try :
im.save("d:/python/temp.jpg")
except :
print("Unexpected error:", sys.exc_info()[0])
pass
# shutil.copy("d:/python/temp2.png","d:/python/temp.png")
f.seek(0)
time.sleep(1)
yield f.read() #Camera.imgs[int(time.time()) % 3]