- An SLDReader that parses an SLD document into a style object.
- A function createOlStyleFunction that converts the parsed style object into a function that you can use in OpenLayers to style features.
The OpenLayers style converter tries to be as efficient as possible by recycling OpenLayers Style instances whenever possible.
More information about the standards:
See docs/examples folder, to serve them locally
Restrictions on supported SLD Features
The SLDReader library can read both SLD v1.0 and SLD v1.1 documents, but not every part of the SLD standard is (or can be) implemented by the SLDReader and OpenLayers style converter (yet).
Marks with well known symbol names are supported: circle, square, triangle, star, cross, x, hexagon, octagon. ExternalGraphic icons are supported.
Wellknown names that reference a symbol library, like
ttf://CustomFont#42 are not supported. The Size and Rotation elements may be dynamic by using the PropertyName element.
Only one Graphic per PointSymbolizer is supported. Each Graphic can only have one Mark or one ExternalGraphic.
Only these static css-parameters are supported:
GraphicStroke with Mark or ExternalGraphic is mostly supported. GraphicFill and PerpendicularOffset are not supported.
Note about GraphicStroke
ExternalGraphic is mostly supported with these caveats:
- The InitialGap property is not supported.
- Always add a Size-element, even if using an ExternalGraphic instead of a Mark.
- SLD V1.0.0 does not officially support the Gap property. For this, SLDReader implements the same workaround that Geoserver uses. You can use the
stroke-dasharrayparameter to add a gap between stroke marks. To do this, use a dash array with two parameters: the first parameter being the size of the graphic and the second being the gap size. See the " GraphicStroke: ExternalGraphic" example.
GraphicStroke vendor options
The following QGIS vendor options are supported on line symbolizers with a graphic stroke:
See the demo page for an example.
Polygons with static fill and stroke style parameters are supported. See LineSymbolizer above for supported stroke css-parameters. GraphicFill is also supported. GraphicStroke with Mark or ExternalGraphic is supported.
Dynamic Labels (with PropertyName elements), Font and Halo are supported. No vendor-specific options are supported. LabelPlacement or PointPlacement are supported. Graphic elements to display behind the label text are not supported.
- For PointPlacement, Displacement is supported1.
- For PointPlacement, Rotation is supported1. PropertyName as rotation value is supported.
- For PointPlacement, AnchorPoint is partially supported. Since OpenLayers does not support fractional anchor points, the label anchor is snapped to the alignment closest to left/right/top/bottom/center alignment. For instance: an
AnchorPointXof 0.1 is snapped to 0, corresponding to left alignment in OpenLayers.
- For LinePlacement, PerpendicularOffset is not supported.
: according to the SLD-spec, label rotation takes place before displacement, but OpenLayers applies displacement before rotation. Beware when combining rotation and displacement inside a single text symbolizer.
Dynamic parameter values
According to the SLD spec, most values can be mixed type (a combination ofplain text and Filter expressions). This means that most values can depend on a feature's properties. The SLDReader only supports dynamic values with PropertyName elements in these cases:
- PointSymbolizer Size
- PointSymbolizer Rotation
- TextSymbolizer Label
Also there is currently no support for arithmetic operators (Add,Sub,Mul,Div).
Units of measure
Only pixels are supported as unit of measure.
The use of a Geometry element to point to a different geometry property on a feature to use for styling is not supported.
The use of Function expressions is not supported.
The SLDReader library supports the following operators inside Filter elements:
Supported OpenLayers version
The SLDReader has a peer dependency on OpenLayers version 5.3.0. Because there are no backwards incompatible changes between v6+ and v5.3, it is possible to use this library in a project that uses a later (v6+) version of OpenLayers.
This may change in the future if the newest version of OpenLayers stops being backwards compatible with this library, or when a juicy new must-have feature is introduced. When that happens, SLDReader will be based on that OpenLayers version.
Creating an issue
Please include an example sld and if possible an example feature as GeoJSON.
- node & npm
- docker (optional, for running the live examples yourself)
Before starting on a pull request, please raise a Github issue first to prevent starting work on something we're already planning/working on.
When making a pull request, please:
- Address only a single issue or add a single item of functionality.
- Create a test for your functionality.
- Follow eslint rules and apply prettier.
- Update or add an example.
To install dependencies, test, build and document
npm install npm test npm run build npm run docs docker-compose up (runs doc website on :4000)