.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "auto_examples/edges/plot_contours.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_auto_examples_edges_plot_contours.py>`
        to download the full example code or to run this example in your browser via Binder

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_auto_examples_edges_plot_contours.py:


===============
Contour finding
===============

We use a marching squares method to find constant valued contours in an image.
In ``skimage.measure.find_contours``, array values are linearly interpolated
to provide better precision of the output contours. Contours which intersect
the image edge are open; all others are closed.

The `marching squares algorithm
<http://users.polytech.unice.fr/~lingrand/MarchingCubes/algo.html>`__ is a
special case of the marching cubes algorithm (Lorensen, William and Harvey
E. Cline. Marching Cubes: A High Resolution 3D Surface Construction Algorithm.
Computer Graphics SIGGRAPH 87 Proceedings) 21(4) July 1987, p. 163-170).

.. GENERATED FROM PYTHON SOURCE LINES 18-43



.. image-sg:: /auto_examples/edges/images/sphx_glr_plot_contours_001.png
   :alt: plot contours
   :srcset: /auto_examples/edges/images/sphx_glr_plot_contours_001.png
   :class: sphx-glr-single-img





.. code-block:: Python


    import numpy as np
    import matplotlib.pyplot as plt

    from skimage import measure


    # Construct some test data
    x, y = np.ogrid[-np.pi : np.pi : 100j, -np.pi : np.pi : 100j]
    r = np.sin(np.exp(np.sin(x) ** 3 + np.cos(y) ** 2))

    # Find contours at a constant value of 0.8
    contours = measure.find_contours(r, 0.8)

    # Display the image and plot all contours found
    fig, ax = plt.subplots()
    ax.imshow(r, cmap=plt.cm.gray)

    for contour in contours:
        ax.plot(contour[:, 1], contour[:, 0], linewidth=2)

    ax.axis('image')
    ax.set_xticks([])
    ax.set_yticks([])
    plt.show()


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.154 seconds)


.. _sphx_glr_download_auto_examples_edges_plot_contours.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: binder-badge

      .. image:: images/binder_badge_logo.svg
        :target: https://mybinder.org/v2/gh/scikit-image/scikit-image/v0.23.2?filepath=notebooks/auto_examples/edges/plot_contours.ipynb
        :alt: Launch binder
        :width: 150 px

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: plot_contours.ipynb <plot_contours.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: plot_contours.py <plot_contours.py>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_