flask jinja templates

flask jinja templates

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(dynamic image)

<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

debug jinja2 html

Realtime Video

index.html

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

main.py

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

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# 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

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<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.
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