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

    Click :ref:`here <sphx_glr_download_examples_plot_color_code.py>` to download the full example code
.. rst-class:: sphx-glr-example-title

.. _sphx_glr_examples_plot_color_code.py:

Vector field color coding
=========================

Demonstration of colormap application to a vector field.

Pyimof provides the :func:`pyimof.display.plot` that displays a color
mapping applyed to a dense vector field according to its orientation
and magnitude. Any circular colormap can be applyed. Matplotlib
provides some of them by default: ``hsv``, ``twilight``,
``twilight_shifted``, ``hsv_r``, ``twilight_r``,
``twilight_shifted_r``.

If no colormap is provided to the :func:`pyimof.display.plot`
function, the fector field color coding is made by constructing a HSV
image in which the hue is the orientation of the vector flow and the
value is its magnitude. The saturation is set to 1.

Pyimof defines the ``middlebury`` matplotlib colormap that is inspired
by the color coding introduced by the Middlebury optical flow
evaluation website__ for displaying algorithms results. Its reverse
version ``middlebury_r`` is also provided.

.. __: http://vision.middlebury.edu/flow/



.. image:: /examples/images/sphx_glr_plot_color_code_001.png
    :class: sphx-glr-single-img





.. code-block:: default



    import matplotlib.pyplot as plt
    import pyimof

    # --- Load the Hydrangea sequence

    I0, I1 = pyimof.data.dogdance()

    # --- Estimate the optical flow

    u, v = pyimof.solvers.ilk(I0, I1)

    # --- Display it with different colormaps

    fig = plt.figure(figsize=((9, 10)))
    ax_arr = fig.subplots(3, 2, True, True)
    fig.tight_layout()

    ax0, ax1 = ax_arr[0, :]

    ax0.imshow(I0, cmap='gray')
    ax0.set_axis_off()
    ax0.set_title("Reference image")

    pyimof.display.plot(u, v, ax=ax1, cmap=None)
    ax1.set_title("Vector field to HSV image")

    cmap_list = ['middlebury', 'hsv', 'twilight', 'twilight_shifted']

    for ax, cm in zip(ax_arr[1:, :].ravel(), cmap_list):
        pyimof.display.plot(u, v, ax=ax, cmap=cm)
        ax.set_title(f"'{cm}' colormap")

    plt.show()


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

   **Total running time of the script:** ( 0 minutes  3.931 seconds)


.. _sphx_glr_download_examples_plot_color_code.py:


.. only :: html

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



  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

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


.. only:: html

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

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