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|
"""
=========================================
Embed in a web application server (Flask)
=========================================
When using Matplotlib in a web server it is strongly recommended to not use
pyplot (pyplot maintains references to the opened figures to make
`~.matplotlib.pyplot.show` work, but this will cause memory leaks unless the
figures are properly closed).
Since Matplotlib 3.1, one can directly create figures using the `.Figure`
constructor and save them to in-memory buffers. In older versions, it was
necessary to explicitly instantiate an Agg canvas (see e.g.
:doc:`/gallery/user_interfaces/canvasagg`).
The following example uses Flask_, but other frameworks work similarly:
.. _Flask: https://flask.palletsprojects.com
"""
import base64
from io import BytesIO
from flask import Flask
from matplotlib.figure import Figure
app = Flask(__name__)
@app.route("/")
def hello():
# Generate the figure **without using pyplot**.
fig = Figure()
ax = fig.subplots()
ax.plot([1, 2])
# Save it to a temporary buffer.
buf = BytesIO()
fig.savefig(buf, format="png")
# Embed the result in the html output.
data = base64.b64encode(buf.getbuffer()).decode("ascii")
return f"<img src='data:image/png;base64,{data}'/>"
# %%
#
# Since the above code is a Flask application, it should be run using the
# `flask command-line tool <https://flask.palletsprojects.com/en/latest/cli/>`_
# Assuming that the working directory contains this script:
#
# Unix-like systems
#
# .. code-block:: console
#
# FLASK_APP=web_application_server_sgskip flask run
#
# Windows
#
# .. code-block:: console
#
# set FLASK_APP=web_application_server_sgskip
# flask run
#
#
# Clickable images for HTML
# -------------------------
#
# Andrew Dalke of `Dalke Scientific <http://www.dalkescientific.com>`_
# has written a nice `article
# <http://www.dalkescientific.com/writings/diary/archive/2005/04/24/interactive_html.html>`_
# on how to make html click maps with Matplotlib agg PNGs. We would
# also like to add this functionality to SVG. If you are interested in
# contributing to these efforts that would be great.
|
