Step 3 - Render images
-----------------------

Once we have our txt file in ``FORMULAS/TXT/`` we must obtain the subindex that Manim gives each formula, for that we will use the file ``export_images.py`` that is in the ``FORMULAS/`` folder.

This file is not made to be edited in its entirety, only certain parts, when opening it, the first lines are as follows:

.. code-block:: python
    :linenos:

    from manimlib.imports import *
    from io import *

    # OPTIONS
    FILE = "quadratic"
    TEX_CLASS = TexMobject

    SCALE = 0.016
    NUMBER_DIRECTION = DOWN
    NUMBER_BUFF = 0.01
    FORMULA_NUMBER_HEIGHT = 0.7


In ``FILE`` we write the name of the txt file that contains the list of formulas (without the txt extension).

In ``TEX_CLASS`` we write ``TexMobject``, ``TextMobject`` or ``Text``, in the case of formulas we write ``TexMobject``, but if we want to include plain text with formulas we use ``TextMobject``. That is:

.. code-block:: python

    formula = TextMobject("$\\frac{x^2}{y}$ This is a inline formula")

.. math::
    \mbox{$\frac{x^2}{y}$ This is a inline formula}

.. code-block:: python

    formula = TextMobject("$\\displaystyle\\frac{x^2}{y}$ This is a displayed formula")

.. math::
    \mbox{$\displaystyle\frac{x^2}{y}$ This is a displayed formula}


Once the changes are made, open a terminal in the Manim main directory (where manim.py is) and execute this code as:

.. code-block::

    python -m manim FORMULAS/export_images.py -s

This will generate a folder in ``FORMULAS`` that will have the same name as the txt file (in capital letters) and a subfolder called ``IMAGES``, like this:

.. code-block::

    FORMULAS
    ├── QUADRATIC
    │   └── IMAGES
    │       ├── im_1.png
    │       ├── ....
    │       └── im_15.png
    └── TXT
        └── quadratic.txt

In the ``IMAGES/`` folder you are going to create the images that we are going to use to enter the real subscripts to make the animations.

The remaining parameters are as follows:

* ``SCALE = 0.016``: It is the scale of the subscripts with respect to the size of the entire formula, that is, the subscripts are :math:`1.6\%` of the size of the entire formula.
* ``NUMBER_DIRECTION = DOWN``: The direction where the indices will be located, that is ``DOWN``, ``UP``, ``LEFT`` or ``RIGHT``.
* ``NUMBER_BUFF = 0.01``: Distance between each element of the formula and its subindex.
* ``FORMULA_NUMBER_HEIGHT = 0.7``: It is the size (height) of the formula number.

.. image:: /_static/img2.png