This topic provides an overview of symbols, renderers, and styles and describes how they work in ArcGIS Runtime. The following topics describe other aspects of working with these objects:
- Symbol types —Describes the available types of symbols in ArcGIS Runtime
- Symbolize data—Describes how to symbolize your data, including code examples
A symbol defines display properties for features and graphics (collectively referred to as geoelements). A geoelement has a geometry (location and shape), optional descriptive information, and a symbol to define display characteristics such as color, size, border, transparency, and so on. It's important to remember, therefore, that a symbol is not the item being represented on the map. Instead, a symbol controls how those items (graphics or features) appear. The relationship is similar, for example, between the words you are reading now (the content) and the font that is used to display them (presentation). Changing the font style, size, and color will not change the meaning of the text but is likely to have an impact on the effectiveness of the presentation. Likewise, the quality of a map's presentation can improve with the proper use of symbols to convey information. Sometimes, the symbol used by a geoelement is contained in a renderer.
A renderer is a collection of one or more symbols. When applied to a layer or graphics overlay, a renderer displays geoelements using the appropriate symbol. If it contains more than a single symbol, a renderer uses logic to determine the symbol to apply to each geoelement, based on one or several attribute values. ArcGIS Runtime also contains a set of raster renderers for displaying rasters according to their cell values.
Some layer types don't support symbols or renderers, such as WMS and vector tile layers. These layers provide styles as an alternative method for changing how features are displayed. As with symbols and renderers, styles determine how a layer's content is presented.
You can apply a symbol directly to individual graphics. You can also use symbols to create a renderer for graphics overlays or feature layers. Symbols, however, cannot be assigned directly to a feature. Symbols can only be applied to features through the use of a renderer assigned to the layer that contains them.
For features and graphics to appear on a map, they must be assigned a symbol. There are a variety of symbol types you can create to display geoelements, with properties such as color, size, and symbol style that you can modify. While each symbol type requires a specific geometry type (point, line, or polygon), you are not restricted to use those symbols exclusively for a given geometry. If you're symbolizing a line, for example, you can choose to use a marker symbol to display the line's vertices (points). Also, symbols may have different capabilities when used in 2D (map) or 3D (scene). To learn more about working with the available symbol types, see Symbol types.
ArcGIS Runtime uses the following two distinct models for symbols, based on the underlying data source:
- Simple symbols follow the web map specification. You can create these symbols through the simple symbology API, or get them from web maps and feature services when advanced symbology is turned off.
- Advanced symbols follow the ArcGIS Pro symbol model. You can create them through ArcGIS Runtime multilayer symbol classes, or get them from feature services, mobile style files, dictionary renderers, and mobile map packages.
Simple symbology is the symbology of the web map. When authoring maps in ArcGIS Pro as web maps, your symbols will be converted to simple symbols. In general, point symbols are converted to picture marker symbols optimized for the web, and line and polygon symbols are simplified while representing the original symbol as closely as possible.
If your app works primarily with web maps that you want to look the same throughout the platform, your app should use the simple symbols API. If you use multilayer symbols and try to save your map as a web map, the save will fail. Forcing it to save drops the symbols.
If your maps are used only with ArcGIS Runtime and ArcGIS Pro, you can use multilayer symbols. Multilayer (advanced) symbols are vectorized in these environments, thereby scaling better on devices with high resolution screens.
For details about specific symbols available in ArcGIS Runtime and examples of their use, see Symbol types.
A renderer contains a set of symbols and controls how data in a layer (or graphics overlay) are displayed. Renderers use data values (from an attribute or raster cell) to determine the symbol to apply. There are a variety of renderer types, some for geoelements and some for rasters, each designed to use a different rendering logic.
Renderers are always used to symbolize feature or raster layers, since symbols cannot be applied directly to that data. A renderer can also be applied to a graphics overlay but may not be appropriate if the overlay has graphics of mixed geometry types. For such a scenario, applying the appropriate symbol directly to each graphic may be the preferred workflow.
Renderers can be updated at run time, allowing your user to dynamically visualize data in the map.
The following are the types of renderers available for geoelements in ArcGIS Runtime:
- Simple—Displays all features in a layer or graphics overlay using the same symbol. For example, display all points in the world cities layer as a small red square.
- Unique value—Applies a unique symbol for each specified value for an attribute (or combination of attributes). A unique value renderer can be based on any data type but is generally used with string attributes. For example, display points in the world cities layer using two symbols: a small gray triangle for features with a value of N for the CAPITAL attribute and a large yellow star for those with a value of Y.
- Class breaks—Symbolizes geoelements according to specific ranges of values for an attribute. The attribute used for a class breaks renderer must be numeric. For example, display world cities with three different symbols: a small blue circle for cities with a value between 0 and 100000 for the POPULATION attribute, a slightly larger blue circle for cities with a POPULATION value between 100001 and 2999999, and a larger blue circle for cities with a value over 3000000.
- Dictionary—Renders geoelements by constructing multilayer symbols from a style file and associated attribute values. This renderer is commonly used to display military symbology.
The following image shows a layer with a class breaks renderer. The renderer displays features as five classes of population, each with a different symbol (a darker or lighter shade of red).
The following raster renderers are available to control how raster data is presented.
- Hillshade—Creates a grayscale 3D representation of an elevation surface, with the sun's (hypothetical) position taken into account for shading the image. It can be applied to a raster layer created with single-band raster data.
- Blend—Blends a hillshade image (derived from the raster) with the original raster. This provides a look similar to the original raster but with some terrain shading, for a rich, textured look.
- Colormap—Provides a discrete mapping of raster pixel values to colors. All pixels matching the specified value are rendered using the mapped color. This can be useful for tasks such as land classification.
- Stretch—Displays continuous raster cell values across a gradual ramp of colors. Use the stretch renderer to draw a single band of continuous data. The stretch renderer works well when you have a large range of values to display, such as in imagery, aerial photographs, or elevation models.
- RGB—Uses the same methods as the stretch renderer but allows you to combine bands as red, green, and blue composites.
Some layers that don’t support symbols and renderers, such as ArcGIS vector tiled layers and WMS, offer styles as a way to control the display of the features they contain. These layers use a default style and also provide the option to apply other available styles.
The styles described here are not the styles you can create using ArcGIS Pro (.stylx file). For information about reading symbols from such a style file, see Read symbols from a map or style file.
ArcGIS vector tiled layer styles
An ArcGIS vector tile layer consumes vector tiles and an associated style for drawing them. Because the style is separate from the underlying data, you can customize the style of an existing basemap layer. There are layers with many styles available through ArcGIS Online.
You can create your own style with the online style editor. Your customized vector layers can then be saved to and read from ArcGIS Online.
WMS servers provide clients with a list of supported styles for each layer. At run time, you can choose the style the WMS server uses to render map images. In general, styles are predefined and cannot be changed or added to.
The styles defined in the layer information can be inspected to determine the styles (if any) that are available. The style of a WMS sublayer can be set to one of the available styles.