.. _css_examples_randomfills:

Fills with randomized symbols
=============================

It is possible to generate fills by randomly repeating a symbol in the polygons to be filled.
Please refer to the :ref:`equivalent SLD chapter <randomized>` for details on the meaning of the various options.

Simple random distribution
--------------------------

Here is an example distributing up to 50 small "slash" symbols in a 100x100 pixel tile (in case of conflicts the symbol will be skipped), enabling random symbol rotation), and setting the seed to "5" to get a distribution different than the default one:

.. code-block:: css

    * {
      fill: symbol("shape://slash");
      :fill {
        size: 8;
        stroke: blue;
        stroke-width: 4;
        stroke-linecap: round;
      };
      stroke: black;
      fill-random: grid;
      fill-random-seed: 5;
      fill-random-rotation: free;
      fill-random-symbol-count: 50;
      fill-random-tile-size: 100;
    }
    
.. figure:: ../../sld/extensions/images/random-slash.png
   :align: center
   
   *Random distribution of a diagonal line*

Thematic map using point density
--------------------------------

Randomized distributions can also be used for thematic mapping, for example, here is the SLD for a version of topp:states that displays the number of inhabitantìs varying the density of a random point distribution:

.. code-block:: css

    * { 
      fill: symbol("circle");
      stroke: black;
      fill-random: grid; 
      fill-random-tile-size: 100;
    
      :fill {
        size: 2;
        fill: darkgray;
      };
      /* @title low */
      [PERSONS < 2000000] {
        fill-random-symbol-count: 50;
      };
      /* @title mid */
      [PERSONS >= 2000000] [PERSONS < 4000000] {
        fill-random-symbol-count: 150;
      };
      /* @title high */
      [PERSONS >= 4000000] {
        fill-random-symbol-count: 500;
      }
    }

    

.. figure:: ../../sld/extensions/images/states-random.png
   :align: center
   
   *Thematic map via point density approach*