.. _export-animation:

Export an animation
==============================

.. note::
   This document is part of a series teaching how to :ref:`create-image-sea-surface-speeds`

.. note::
   Before you export to any format, you might want to :ref:`set-view-size`.


.. warning::
   Before you start exporting :ref:`save-state`. Things can go wrong and often you want to reproduce a saved animation (with small changes).


It has proven useful to export to a sequence of png files that can then be concatenated using ``ffmpeg``.

Chose ``File->Save Animation``, enter a base file name (will be expanded by _0123/..., see the ``Suffix format`` field in the following dialogue), and ensure the correct image size in the following dialogue.


.. image:: export-basic-screen.png


(If you change the size of the saved animation, you might want to toggle the gear in the top left and change the font scaling option, but really -- :ref:`set-view-size` beforehand!)

.. image:: export-advanced-screen.png


This will generate a sequence of .png files. For a quick impression you can run through them using ``eog FILENAME*.png`` on linux, or preview on a mac.


.. note::
   FFMPEG is not included in the software image on the VM of the 2020 ESiWACE2 HPDA and Vis course. On DKRZ's supercomputer mistral you can find a reasonable ffmpeg on the GPU nodes.

If you have a reasonably complete ffmpeg, this shell script will work:

.. code-block:: bash

   #!/bin/bash
   set -evxu
   output_framerate=${output_framerate:-5}
   ffmpeg -framerate $output_framerate -pattern_type glob -i "$1"  -c:v libx264 -r $output_framerate -pix_fmt yuv420p $2
   echo created $2


Save it as ``ffmglob``, do ``chmod a+x ffmglob`` to make it executable and then call it as ``./ffmglob 'FILENAME*.png' speeds.mp4`` -- yes, you need the quotes around the FILENAME expression.

This is the end of the example :ref:`create-image-sea-surface-speeds`. Next you could  continue with :ref:`display-transparent-clouds`.