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geonode-training

Optimizing, publishing and styling Vector data

Styling with CSS

The CSS extension module allows to build map styles using a compact, expressive styling language already well known to most web developers: Cascading Style Sheets.

The extension is available on GeoServer only. The standard CSS language has been extended to allow for map filtering and managing all the details of a map production. In this section we’ll experience creating a few simple styles with the CSS language.

Styling vector data

Creating line styles

Go to the mainrd layer details page and click on Editing Tools > Style > Edit
Add a new Style; select CSS and click on the + button
Name it CSS Roads and Save
Edit the new style

Switch to text mode and insert the following CSS

  * {
    stroke: orange;
    stroke-width: 6;
    stroke-linecap: round;
  }

Now let’s create a cased line effect by adding a second set of colours and widths, and forcing two different z indexes for them. Rewrite the CSS as follows
```
  * {
    stroke: orange, yellow;
    stroke-width: 6, 2;
    stroke-linecap: round;
    z-index: 1, 2;
  }
```
Notice the two strokes of different size look like the border of a highway.

Let’s add a label that follows the road. Rewrite the CSS as follows

  * {
    stroke: orange, yellow;
    stroke-width: 6, 2;
    stroke-linecap: round;
    z-index: 1, 2;
    label: [LABEL_NAME];
    font-fill: black;
    font-family: Arial;
    font-size: 12;
    font-weight: bold;
    halo-color: white;
    halo-radius: 2;
    -gt-label-follow-line: true;
    -gt-label-group: true;
    -gt-label-repeat: 400;
    -gt-label-max-displacement: 50;
  }

Notice how compact is the CSS syntax versus the SLD one. It is also much more intuitive. While writing the CSS the text editor is also able to hilight typeahead hints.

Creating point styles

Go to the pointlm layer details page and click on Editing Tools > Style > Edit
Add a new Style; select CSS and click on the + button
Name it CSS Landmarks and Save
Edit the new style

Switch to text mode and insert the following CSS

  * {
    mark: symbol('circle');
    mark-size: 5;
  }

Let’s change the color of the points by specifying a fill. If we specified a fill in the top level rule it would be interpreted as a polygonal fill, to express that we want to fill inside the marks we have to create a new rule with the :mark pseudo-selector
```
  * {
    mark: symbol('circle');
    mark-size: 5;
  }

  :mark {
    fill: cyan;
    stroke: darkblue;
  }
```

Finally, let’s override the default styling for all shopping centers. Shopping centers are not easy to find, they have a MTFCC category value equal to C3081 and contain Shopping in the name.

  * {
    mark: symbol('circle');
    mark-size: 5;
  }

  :mark {
    fill: cyan;
    stroke: darkblue;
  }

  [MTFCC = 'C3081' AND FULLNAME LIKE '%Shopping%'] {
    mark: url("./img/landmarks/shop_supermarket.p.16.png");
    mark-size: 16;
  }

Creating polygon styles

As test_user1, upload a the ESRI Shapefile named ne_50m_admin_0_countries from the folder /opt/data/sample_data/user_data
Add a new CSS style to the new layer names CSS Population

We want to create a simple 3 class thematic map based on the country population, stored in the POP_EST attribute

  [POP_EST < 10000000] {
    fill: lightgrey;
  }

  [POP_EST >= 10000000 AND POP_EST < 50000000] {
    fill: olive;
  }

  [POP_EST > 50000000] {
    fill: salmon
  }

Let’s also add a very thin black border around all polygons, regardless of their population, using the * selector

  [POP_EST < 10000000] {
    fill: lightgrey;
  }

  [POP_EST >= 10000000 AND POP_EST < 50000000] {
    fill: olive;
  }

  [POP_EST > 50000000] {
    fill: salmon
  }

  * {
    stroke: black;
    stroke-width: 0.2;
  }

Patterns and Hatches

Upload the ESRI Shapefile named tl_2010_08013_arealm from the folder /opt/data/sample_data/pretty_maps/data/boulder
Create a new CSS style named CSS Area Landmarks for the tl_2010_08013_arealm layer
Switch to the text editor insert the following CSS
```
  [MTFCC='K2582'] [@scale < 500000] {
      fill: url(./img/landmarks/area/grave_yard.png);
      fill-mime: 'image/png';
  }
```
_The above CSS defines a with a pointing to a png ./img/landmarks/area/grave_yard.png in the GeoServer data directory, which will be used by GeoServer as pattern to fill the polygon._

The previous example uses a png as fill pattern; the next one uses a font character instead

  [MTFCC='K2582'] [@scale < 500000] {
    fill: #D3FFD3, symbol('ttf://Wingdings#0x0055');
    fill-size: 16;
    fill-opacity: 0.5, 1.0;
    stroke: #6DB26D;
    -gt-graphic-margin: 8;
    :nth-symbol(2) {
      stroke: #6DB26D;
    }
  }

Let’s now take a look at another way to fill polygons using patterns, the Hatches.
Edit the styles of the GeoNode layer Wetlands_regulatory_areas
Create a new CSS style and name it CSS Regulatory Area

Insert the following CSS

  [@scale < 10000] {
    fill: symbol('shape://times');
    fill-size: 8;
    :nth-symbol(1) {
      stroke: #ADD8E6;
      stroke-width: 1.0;
    };
  }

On the previous example we used times as hatches mark. GeoServer makes available different kinds of hatches marks:

Dashes

Lets now familiarize a bit with Dashes. We are going to see how it’s possible to draw several kind of dashes to represent different types of trails or roads.

Edit the styles of the GeoNode layer Trails
Create a new CSS style and name it CSS Trails