FeatureView Styling

The style of features in a FeatureView asset are specified using rules defined in a JavaScript object. Style can be set during initial definition of a FeatureViewLayer or anytime after. The styling system allows you to set broad style rules that apply to large groups of features, as well as more specific rules for particular features. Feature style can be defined by constant values or data driven, based on feature characteristics.

Style object

The basic structure of a style object is shown below. There are two types of rules: broad rules and specific rules. Broad rules affect all features in a FeatureView asset, while specific rules affect a subset of features.

{
  // Broad style rules.
  opacity: …,
  polygonFillColor: …,

  // Specific style rules.
  rules: [
    { … },
    { … }
  ]
};

Broad rules

To apply style properties to all features (or those of a specific geometry type), specify the style properties at the top level in the style object.

{
  opacity: 0.5,
  pointShape: 'triangle',
  lineWidth: 10,
  polygonFillColor: 'green'
};

Specific rules

To apply style properties to a subset of features, use the rules field. The rules field accepts a list of JavaScript objects, each with a filter that selects features according to conditions defined by an ee.Filter object, followed by a series of style properties. In the example below, there is a rule that sets polygonStrokeWidth and polygonFillColor only if the "REP_AREA" property is less than 100. Specific rules override the style properties of broad rules, and rules near the end of the rules list override those near the beginning (specific rules are evaluated first to last).

{
  rules: [
    {
      filter: ee.Filter.lt('REP_AREA', 100),
      polygonStrokeWidth: 0.5,
      polygonFillColor: 'blue'
    },
    { … }  // Optionally include additional rules.
  ]
};

Setting style

Feature style can be set when a FeatureViewLayer is declared or anytime after.

FeatureViewLayer declaration

To set the visualization parameters when declaring a FeatureViewLayer, use the visParams parameter.

var visParams = {
  opacity: 0.5,
  lineWidth: 10,
  polygonFillColor: 'purple'
};

var layer = ui.Map.FeatureViewLayer({
  assetId: 'WCMC/WDPA/current/polygons_FeatureView',
  visParams: visParams
});

Map.add(layer);

Existing FeatureViewLayer

To set the visualization parameters for an existing FeatureViewLayer, use the setVisParams function. It replaces any previously specified style rules; unspecified properties are set to their default.

var layer = ui.Map.FeatureViewLayer('WCMC/WDPA/current/polygons_FeatureView');
Map.add(layer);

layer.setVisParams({
  opacity: 0.5,
  lineWidth: 10,
  polygonFillColor: 'purple'
});

Symbology

For each style property, you can specify either a constant style rule or a data-driven style rule. The data-driven option uses feature property values to determine symbolization, which can either be categorical or interpolated. For a full list of the style properties, see the style properties table.

Constant

A constant style rule consists of a style property to set and its value. The following example sets the polygon fill color to blue.

var visParams = {
  polygonFillColor: 'blue'
};

Categorical

A categorical style rule consists of a style property to set and a JavaScript object with three properties:

• property — a feature property name whose value will affect the style.
• categories — a list of lists that map feature property values to style property symbologies. Each category includes a property value followed by a symbology value to apply. The property value that defines a category must be a string.
• defaultValue — a default symbology to apply to features whose property value is not defined in categories. If it is null/undefined, default style settings will be applied.

For example, the following object sets the color style property based on the "MARINE" feature property. Features in "MARINE" category "0" are set as purple, "1" as green, "2" as blue, and any other category as white.

var visParams = {
  color: {
    property: 'MARINE',
    categories: [
      ['0', 'purple'],
      ['1', 'green'],
      ['2', 'blue']
    ],
    defaultValue: 'white'
  }
};

Interpolated

An interpolated style rule consists of a style property to set and a JavaScript object with up to five properties:

• property — a feature property name whose value will affect the style.
• mode — the interpolation mode, either 'linear' or 'interval'.
• palette — a list of colors, opacities, or widths to interpolate input property values between. The format depends on the mode, see the Linear and Interval sections for more details.

Applies only to 'linear' mode

• min — the property value to map to the first element in the palette list.
• max — the property value to map to the last element in the palette list.

Linear

Linear interpolation mode sets a feature style property by mapping input values in the range min to max linearly between a list of symbology values defined in the palette property. The input values are clamped to the range set by min and max.

For example, the following object sets the color style property based on the "REP_AREA" feature property. The palette property is a list of colors indicating that input values between min and max should grade linearly from yellow to red to blue. A value between 1 and 500 is interpolated between yellow and red, and a value between 500 and 1000 is interpolated between red and blue.

var visParams = {
  color: {
    property: 'REP_AREA',
    mode: 'linear',
    palette: ['yellow', 'red', 'blue'],
    min: 1,
    max: 1000
  }
};

Interval

Interval interpolation mode sets a feature style property by mapping input values to class breaks and then applying a class-specific symbology. Input values from the selected feature property are assigned to the nearest class break value by rounding down. The palette property is formatted as a list of lists, where each inner list contains a class break value followed by a style property value. Features whose property value are less than the minimum class break value maintain their default style property setting.

In the following example, feature fill opacity is set according to graduated classes of the "REP_AREA" property. Class definition and style symbology are provided in the palette property as a list of lists. It indicates that there should be 4 classes with breaks at value 0, 80, 2000, and 5000, with respective feature opacities of 0.5, 0.35, 0.22, and 0.15. In other words, features with "REP_AREA" values in the interval $ 0 \le x < 80 $ will have a fill opacity of 0.5, values in the interval $ 80 \le x < 2000 $ will have fill opacity of 0.35, and so on.

var visParams = {
  fillOpacity: {
    property: 'REP_AREA',
    mode: 'interval',
    palette: [
      [0, 0.5],
      [80, 0.35],
      [2000, 0.22],
      [5000, 0.15]
    ]
  }
};

All style properties

Below are all of the style properties you can specify in the style object. Setting style properties for specific geometry types overrides the corresponding style properties set for "All geometries" (for example, setting polygonFillColor overrides the value set in fillColor).