.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "gallery/user_interfaces/canvasagg.py" .. LINE NUMBERS ARE GIVEN BELOW. .. only:: html .. meta:: :keywords: codex .. note:: :class: sphx-glr-download-link-note :ref:`Go to the end ` to download the full example code .. rst-class:: sphx-glr-example-title .. _sphx_glr_gallery_user_interfaces_canvasagg.py: ============== CanvasAgg demo ============== This example shows how to use the agg backend directly to create images, which may be of use to web application developers who want full control over their code without using the pyplot interface to manage figures, figure closing etc. .. note:: It is not necessary to avoid using the pyplot interface in order to create figures without a graphical front-end - simply setting the backend to "Agg" would be sufficient. In this example, we show how to save the contents of the agg canvas to a file, and how to extract them to a numpy array, which can in turn be passed off to Pillow_. The latter functionality allows e.g. to use Matplotlib inside a cgi-script *without* needing to write a figure to disk, and to write images in any format supported by Pillow. .. _Pillow: https://pillow.readthedocs.io/ .. redirect-from:: /gallery/misc/agg_buffer .. redirect-from:: /gallery/misc/agg_buffer_to_array .. GENERATED FROM PYTHON SOURCE LINES 26-60 .. code-block:: Python from PIL import Image import numpy as np from matplotlib.backends.backend_agg import FigureCanvasAgg from matplotlib.figure import Figure fig = Figure(figsize=(5, 4), dpi=100) # A canvas must be manually attached to the figure (pyplot would automatically # do it). This is done by instantiating the canvas with the figure as # argument. canvas = FigureCanvasAgg(fig) # Do some plotting. ax = fig.add_subplot() ax.plot([1, 2, 3]) # Option 1: Save the figure to a file; can also be a file-like object (BytesIO, # etc.). fig.savefig("test.png") # Option 2: Retrieve a memoryview on the renderer buffer, and convert it to a # numpy array. canvas.draw() rgba = np.asarray(canvas.buffer_rgba()) # ... and pass it to PIL. im = Image.fromarray(rgba) # This image can then be saved to any format supported by Pillow, e.g.: im.save("test.bmp") # Uncomment this line to display the image using ImageMagick's `display` tool. # im.show() .. GENERATED FROM PYTHON SOURCE LINES 61-71 .. admonition:: References The use of the following functions, methods, classes and modules is shown in this example: - `matplotlib.backends.backend_agg.FigureCanvasAgg` - `matplotlib.figure.Figure` - `matplotlib.figure.Figure.add_subplot` - `matplotlib.figure.Figure.savefig` / `matplotlib.pyplot.savefig` - `matplotlib.axes.Axes.plot` / `matplotlib.pyplot.plot` .. _sphx_glr_download_gallery_user_interfaces_canvasagg.py: .. only:: html .. container:: sphx-glr-footer sphx-glr-footer-example .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: canvasagg.ipynb ` .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: canvasagg.py ` .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_