Styling layers

Understanding layer styles

A layer's style is defined in a JSON-based called the Felt Style Language, or FSL for short. Editors can view the current style of a layer inside a Felt map by clicking on Actions > Edit styles in a layer's overflow menu (three dots).

Here is an example of a simple visualization, expressed in FSL:

{
  "config": {"labelAttribute": ["type"]},
  "legend": {},
  "paint": {
    "color": "blue",
    "opacity": 0.9,
    "size": 30,
    "strokeColor": "auto",
    "strokeWidth": 1
  },
  "type": "simple",
  "version": "2.1"
}

Fetching a layer's current style

A layer's FSL can be retrieved by performing a simple GET request to a layer's endpoint:

curl

# Your API token should look like this:
# FELT_API_TOKEN="felt_pat_ABCDEFUDQPAGGNBmX40YNhkCRvvLI3f8/BCwD/g8"
FELT_API_TOKEN="<YOUR_API_TOKEN>"
MAP_ID="<YOUR_MAP_ID>"
LAYER_ID="<YOUR_LAYER_ID>"

curl -L \
  -H "Authorization: Bearer ${FELT_API_TOKEN}" \
  "https://felt.com/api/v2/maps/${MAP_ID}/layers/${LAYER_ID}"

Python

felt-python

Updating an existing layer's style

To update a layer's style, we can send a POST request with the new FSL to the same layer's /update_style endpoint.

curl

curl -L \
  -X POST \
  "https://felt.com/api/v2/maps/${MAP_ID}/layers/${LAYER_ID}/update_style" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer ${FELT_API_TOKEN}" \
  --data '{"style": {"paint": {"color": "green", "opacity": 0.9, "size": 30, "strokeColor": "auto", "strokeWidth": 1}, "legend": {}, "type": "simple", "version": "2.1"}}'

Python

felt-python

FSL examples

You can find examples of FSL for different visualization types in the Felt Style Language section of these docs:

• Simple visualizations: same color and size for all features (vector) or pixels (raster).

• Categorical visualizations: different color per feature or pixel, based on a categorical attribute

• Numeric visualizations: different color or size per feature or pixel, based on a numeric attribute.

• Heatmaps: a density-based visualization style, for vector point layers.

• Hillshade: a special kind of visualization for raster elevation layers.