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tutorial to use python flask jinja templates and a realtime video demo

Guide

Jinja delimiters

The default Jinja delimiters are configured as follows:

{% ... %} for Statements

{{ ... }} for Expressions to print to the template output

{# ... #} for Comments not included in the template output

#  ... ## for Line Statements

url_for static(css+image)

<link rel="stylesheet" type="text/css" href="{{ url_for('static', filename='bootstrap/bootstrap.min.css') }}">

<img src="{{ url_for('static', filename='images/1.PNG') }}" height="{{query_img_height}}" width="{{query_img_width}}">

You have by default the static endpoint for static files.

will be converted to

<link rel="stylesheet" type="text/css" href="/static/bootstrap/bootstrap.min.css">

<img src="/static/images/1.PNG" height="1799" width="896">

url for static(pass image path)

<h1>Image  {{image_filename}}</h1>

<img src="{{ url_for('static', filename = image_filename) }}" height="{{query_img_height}}" width="{{query_img_width}}">

notice we do't use

filename = {{image_filename}}

image_filename will be passed to html with value images/1.PNG

will be converted to

<h1>Image  images/1.PNG </h1>

<img src="/static/images/1.PNG" height="1799" width="896">

filter

{% set result_count = result_list | length %}

{{ index | string ) }}

filter: length, string

debug html

url_for with params

python code

@app.route('/index')

@app.route('/')

def index():

    return 'you are in the index page'

@app.route('/questions/<int:question_id>'):

#int has been used as a filter that only integer will be passed

# in the url otherwise it will give a 404 error

def find_question(question_id):

    return ('you asked for question {0}'.format(question_id))

html page

<a href={{ url_for('index') }}>Index</a>

<a href = {{ url_for('find_question' ,question_id=1) }}>Question 1</a>

{% if kline_chart %}

   <div class="chart">{{ kline_chart | safe }}</div>

{% endif %}

Realtime Video

index.html

<img src="{{ url_for('video_feed') }}" height="480" width="640">

main.py

#===================================================

outputFrame = None

lock = threading.Lock()

# initialize a flask object

app = Flask(__name__)

@app.route("/")

def index():

	# return the rendered template

	return render_template("index.html")

def generate():

    	# grab global references to the output frame and lock variables

	global outputFrame, lock

	# loop over frames from the output stream

	while True:

		# wait until the lock is acquired

		with lock:

			# check if the output frame is available, otherwise skip

			# the iteration of the loop

			if outputFrame is None:

				continue

			# encode the frame in JPEG format

			(flag, encodedImage) = cv2.imencode(".jpg", outputFrame)

			# ensure the frame was successfully encoded

			if not flag:

				continue

		# yield the output frame in the byte format

		yield(b'--frame\r\n' b'Content-Type: image/jpeg\r\n\r\n' +

			bytearray(encodedImage) + b'\r\n')

@app.route("/video_feed")

def video_feed():

	# return the response generated along with the specific media

	# type (mime type)

	return Response(generate(),

		mimetype = "multipart/x-mixed-replace; boundary=frame")

#===================================================

# start the flask app

args = {"ip":"0.0.0.0","port":8888}

app.run(host=args["ip"], port=args["port"], debug=True,

		threaded=True, use_reloader=False)

Example

index

# for web

from flask import Flask,Response,render_template

web_params = {

    "query_key":"",

    "query_segimg_filepath":"",

    "query_segmask_filepath":"",

    "query_img_height":0,

    "query_img_width":0,

    "result_list": []

}

# initialize a flask object

app = Flask(__name__)

@app.route("/")

def index():

    global web_params

    return render_template("search.html",**web_params)

# start the flask app

args = {"ip":"0.0.0.0","port":8888}

app.run(host=args["ip"], port=args["port"], debug=True,threaded=True, use_reloader=False)

index.html

<html>

  <head>

    <title>Query {{query_key}}</title>

  </head>

  <body>

    <h1>Query Image {{ query_segimg_filepath }} </h1>

    {#

      <img src="{{ url_for('static', filename='images/1.PNG') }}"

        height="30"

        width="30">

    #}

    <img src="{{ url_for('static', filename = query_segimg_filepath) }}"

      height="{{query_img_height}}"

      width="{{query_img_width}}">

    {#

      <img src="{{ url_for('static', filename = query_segmask_filepath) }}"

        height="{{query_img_height}}"

        width="{{query_img_width}}">

    #}

    {% set result_count = result_list | length %}

    <h1>Search Results #{{result_count}}</h1>

    {% for i in range(0,result_count) %}

      {% set item = result_list[i] %}

      {% set segimg_filepath = item["segimg_filepath"] %}

      {% set segmask_filepath = item["segmask_filepath"] %}

      {% set img_height = item["height"] %}

      {% set img_width = item["width"] %}

      <h2>Top # {{i}}  {{ segimg_filepath }}</h2>

      <img src="{{ url_for('static', filename = segimg_filepath) }}" height="{{img_height}}" width="{{img_width}}">

      {#

        <img src="{{ url_for('static', filename = segmask_filepath) }}" height="{{img_height}}" width="{{img_width}}">

      #}

    {% endfor %}

  </body>

</html>

Reference

History

20191005: created.

Copyright

Post author: kezunlin
Post link: https://kezunlin.me/post/1e37a6/
Copyright Notice: All articles in this blog are licensed under CC BY-NC-SA 3.0 unless stating additionally.

巴特西

flask的模板引擎jinja入门教程包含一个通过网络实时传输Video视频流的示例

Guide

Jinja delimiters

url_for static(css+image)

url for static(pass image path)

filter

debug html

url_for with params

Realtime Video

index.html

main.py

Example

index

index.html

Reference

History

Copyright

最新文章

热门文章

巴特西

flask的模板引擎jinja入门教程 包含一个通过网络实时传输Video视频流的示例

Guide

Jinja delimiters

url_for static(css+image)

url for static(pass image path)

filter

debug html

url_for with params

Realtime Video

index.html

main.py

Example

index

index.html

Reference

History

Copyright

最新文章

热门文章

flask的模板引擎jinja入门教程包含一个通过网络实时传输Video视频流的示例