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How are text labels positioned in a GeoServer?
Text labels are positioned eoither at points or along linear paths derived from the geometry being labelled. Labelling is a complex operation, and effective labelling is crucial to obtaining legible and visually pleasing cartographic output. For this reason SLD provides many options to control label placement.
Where do I find the text symbolizer in SLD?
The following symbolizer is taken from the Points section in the SLD Cookbook. The symbolizer labels features with the text from the name property. The font is Arial in bold at 12 pt size, filled in purple. The labels are centered on the point along their lower edge, then displaced 25 pixels upwards, and finally rotated 45 degrees counterclockwise.
Can a GeoServer be used as a SLD extension?
GeoServer provides a number of label styling options as extensions to the SLD specification. Using these options gives more control over how the map looks, since the SLD standard isn’t expressive enough to provide all the options one might want. These options are specified as subelements of .
How does the maxdisplacement option work in GeoServer?
The maxDisplacement option controls the displacement of the label along a line, around a point and inside a polygon. For lines, normally GeoServer labels a line at its center point only. If this label conflicts with another one it may not be displayed at all.
Text labels are positioned either at points or along linear paths derived from the geometry being labelled. Labelling is a complex operation, and effective labelling is crucial to obtaining legible and visually pleasing cartographic output. For this reason SLD provides many options to control label placement.
How to apply GeoServer SLD vendor options for label placement?
Label placement is a hard problem (and takes a lot of time and memory) to do well as you have to extract the labels from each layer as they are rendered and then place them at the end of rendering. So I suspect that OpenLayers will never catch up with GeoServer in labelling.
Which is an optional sub element in GeoServer?
The standard SLD LinePlacement element provides one optional sub-element, . GeoServer provides much more control over line label placement via vendor-specific options; see below for details.
How to label a geometry with a textsymbolizer?
Any kind of geometry may be labelled with a . For non-point geometries, a representative point is used (such as the centroid of a line or polygon). The element specifies the text that will be rendered as the label.
What should the font size be in GeoServer?
The above example would display text at different sizes depending on the scale denominator setting. A font size of 12 for scale denominator of less than or equal to 300, a font size of 10 for scale denominator from 300-2500 and a font size of 8 for scale denominator greater than 2500.
What kind of symbols are used in GeoServer?
GeoServer supports the standard SLD symbols, a user-expandable set of extended symbols, and also TrueType Font glyphs. The symbol names are specified in the element.
What is an external graphic file in GeoServer?
External Graphics are image files (in formats such as PNG or SVG) that contain the shape and color information defining how to render a symbol. For GeoServer extensions for specifying external graphics, see Graphic symbology in GeoServer. The element has the sub-elements:
How is a symbol specified in the pointsymbolizer?
The symbol is specified by either an or a element. External Graphics are image files (in a format such as PNG or SVG) that contain the shape and color information defining how to render a symbol. Marks are vector shapes whose stroke and fill are defined explicitly in the symbolizer.