Creating Maps in GeoServer using CSS and SLD - FOSS4G 2021 Edition

The presentation aims to provide attendees with enough information to master GeoServer styling documents and most of GeoServer extensions to generate appealing, informative, readable maps that can be quickly rendered on screen. Examples will be provided from the OSM data directory GeoSolutions shared with the community.

Transcript

1. Creating stunning maps with GeoServer With SLD and CSS Ing. Andrea Aime GeoSolutions 1
2. GeoSolutions • Offices in Italy & US, Clients Worldwide • 30+ collaborators, 25+ Engineers • www.geosolutionsgroup.com • Our products • Our Offer Enterprise Support Services Deployment Subscription Professional Training Customized Solutions GeoNode
3. Affiliations We strongly support Open Source, it Is in our core We actively participate in OGC working groups and get funded to advance new open standards We support standards critical to GEOINT
4. Quick tour of styling languages 4
5. Languages SLD 1.0 core SLD 1.1 core YSLD extension MBStyles community GeoCSS extension SLD 1.0 inspired object model, with extensions parse parse parse parse and translate parse and translate 5 Map rendering
6. Shared concepts • Layer (the styles applies to) • Rules • Filters/selectors (what should be painted) • Scale dependencies (zoomed in, zoomed out?) • Symbolizers (how should it be painted) • Point • Line • Polygon • Text 6
7. Styled Layer Descriptor 1.0 and 11 • The only OGC styling standard • XML based, verbose, hard to hand edit • Was meant for machine export but ended up being edited a lot by hand • Autocomplete in the style editor • Can be generated by external tools and imported • However interoperability is limited • Often needs to be hand tweaked 7
8. SLD 1.0 example <!–- Boilerplate beginning ommitted --> … <sld:Rule> <ogc:Filter> <ogc:PropertyIsEqualTo> <ogc:PropertyName>type</ogc:PropertyName> <ogc:Literal>alpine_hut</ogc:Literal> </ogc:PropertyIsEqualTo> </ogc:Filter> <sld:MaxScaleDenominator>100000.0</sld:MaxScaleDenominator> <sld:PointSymbolizer> <sld:Graphic> <sld:ExternalGraphic> <sld:OnlineResource xlink:type="simple" xlink:href="symbols/alpinehut.p.16.png"/> <sld:Format>image/png</sld:Format> </sld:ExternalGraphic> </sld:Graphic> </sld:PointSymbolizer> </sld:Rule> <!–- Boilerplate end ommitted --> Filter Scale dep. Symbolizer
9. YSLD • SLD in YAML syntax • Filtering by CQL • Can define reusable variables and blocks • Verbosity it’s between SLD and CSS • Has a notion of zoom levels, if needed feature-styles: - rules: - filter: type = 'alpine_hut' scale: (,100000.0) symbolizers: - point: symbols: - external: url: symbols/alpinehut.p.16.png format: image/png 9
10. GeoCSS • Compact syntax, familiar for web developers • CQL based filtering, rule nesting and cascading keeps styling compact • Does not get any more compact than this: • Cons: some are confused by “rule cascading” 🡪 can now be turned off [type = 'alpine_hut'][@sd < 100k] { mark: url('symbols/alpinehut.p.16.png'); } 10
11. MBStyles (aka MapBox GL) • JSON based, designed for GUI editing (like SLD) instead of hand editing • Only Web Mercator zoom level based scale control • Symbols coming from “sprites” (symbol collections) • Unlike others, no styling extensions • No rendering transformations • Limited expressions usage • Pro: can be applied both on the client side and the server side
12. MBStyles (aka MapBox GL) { "version": 8, … boilerplate omitted here "name": "mountain huts" , "sprite": "https://my.sever/sprite" , "layers": [ { "id": "huts", "type": "symbol", "minzoom": 9, "filter": [ "==", "type", "alpine_hut" ], "layout": { "icon-image" : "alpinehut", "icon-size": 1, "icon-allow-overlap" : true } } ] } Filter (in postfix notation!) Scale dep. Symbolizer The sprint contains various images, like in videogames
13. What’s next • Going to explore styling concepts • Languages used in examples • SLD 1.0 + GS extensions • GeoCSS SLD CSS
14. Scale dependencies 14
15. Types of Scale dependency • Decide whether to symbolize based on the scale or not • E.g., at lower scales/lower zoom levels do not show buildings • Symbolize in a different way depending on the scale • E.g., different thickness based on the current zoom
16. Expressing scale dependency filters • SLD: • <MinScaleDenominator> 1000 </MinScaleDenominator> • <MaxScaleDenominator> 1000000 </MaxScaleDenominator> • CSS • [@sd > 1k][@sd < 1M] Compact expression of large numbers makes them readable at a glance, e.g., 100k, 1M , 10M
17. Unit of Measure • Useful if you have real world measures of line thicknesses and the like … <LineSymbolizer uom="http://www.opengeospatial.org/se/units/metre"> <Stroke> <CssParameter name="stroke">#0000FF</CssParameter> <CssParameter name="stroke-width">5</CssParameter> </Stroke> </LineSymbolizer> ... … stroke: blue; stroke-width: 5m; SLD CSS
18. Transformation functions • Another way of setting a different value depending on the current scale/zoom level • Useful if the scaling is not linear [class = 'highway’ and type in ('motorway’, 'motorway_link’)] [@sd < 25M] { stroke: #e66e89; stroke-width: categorize(@sd, 2, 400k, 1.9, 800k, 1.4, 1.5M, 1, 3M, 0.8, 6M, 0.5); • Less than 400k 🡪 2px • [400k, 800k] 🡪 1.9px • [800k, 1.5M] 🡪 1.4px • [1.5M, 3M] 🡪 1 • [3M, 6M] 🡪 0.8 • Above 6M -> 0.5 CSS
19. Transformation functions in SLD <sld:LineSymbolizer> <sld:Stroke> <sld:CssParameter name="stroke">#e66e89</sld:CssParameter> <sld:CssParameter name="stroke-width"> <ogc:Function name="Categorize"> <ogc:Function name="env"> <ogc:Literal>wms_scale_denominator</ogc:Literal> </ogc:Function> <ogc:Literal>2</ogc:Literal> <ogc:Literal>400000</ogc:Literal> <ogc:Literal>1.9</ogc:Literal> <ogc:Literal>800000</ogc:Literal> <ogc:Literal>1.4</ogc:Literal> <ogc:Literal>1500000</ogc:Literal> <ogc:Literal>1</ogc:Literal> <ogc:Literal>3000000</ogc:Literal> <ogc:Literal>0.8</ogc:Literal> <ogc:Literal>6000000</ogc:Literal> <ogc:Literal>0.5</ogc:Literal> </ogc:Function> </sld:CssParameter> </sld:Stroke> </sld:LineSymbolizer> SLD
20. Point styling 20
21. Simple image [type = 'alpine_hut'][@sd < 100k] { mark: url('symbols/alpinehut.p.16.png'); } <sld:Rule> <ogc:Filter> <ogc:PropertyIsEqualTo> <ogc:PropertyName>type</ogc:PropertyName> <ogc:Literal>alpine_hut</ogc:Literal> </ogc:PropertyIsEqualTo> </ogc:Filter> <sld:MaxScaleDenominator>100000.0</sld:MaxScaleDenominator> <sld:PointSymbolizer> <sld:Graphic> <sld:ExternalGraphic> <sld:OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" xlink:type="simple" xlink:href="symbols/alpinehut.p.16.png"/> <sld:Format>image/png</sld:Format> </sld:ExternalGraphic> </sld:Graphic> </sld:PointSymbolizer> </sld:Rule> SLD CSS
22. Marks (SVG in this case) [type = 'bank'][@sd < 6k] { mark: symbol('file://symbols/bank.svg'); :mark { fill: #734a08 }; mark-size: 14; } <sld:Rule> <ogc:Filter> <ogc:PropertyIsEqualTo> <ogc:PropertyName>type</ogc:PropertyName> <ogc:Literal>bank</ogc:Literal> </ogc:PropertyIsEqualTo> </ogc:Filter> <sld:MaxScaleDenominator>6000</sld:MaxScaleDenominator> <sld:PointSymbolizer> <sld:Graphic> <sld:Mark> <sld:WellKnownName>file://symbols/bank.svg</sld:WellKnownName> <sld:Fill> <sld:CssParameter name="fill">#734a08</sld:CssParameter> </sld:Fill> </sld:Mark> <sld:Size>14</sld:Size> </sld:Graphic> </sld:PointSymbolizer> </sld:Rule> CSS bank.svg
23. Marks composition and override [type = 'fountain’] { [@sd < 6k] { mark: symbol(circle), symbol(circle); :nth-mark(1) { fill: #b5d0d0 }; :nth-mark(2) { fill: #576ddf }; mark-size: 10, 3; }; [@sd < 3k] { mark: symbol('file://symbols/fountain.svg'); :mark { fill: #576ddf; }; } } CSS
24. • Many other options! • Built-in symbol names (well known marks): circle, square, triangle, … • From TTF fonts using the name ttf://<fontname>#charcode • Windbarbs, e.g.: windbarbs://default(15)[kts] • WKT specification, e.g. wkt://MULTIPOLYGON(((-0.25 -0.25, -0.125 -0.25), (0.125 -0.25, 0.25 -0.25)), (-0.25 0.25, -0.125 0.25), (0.125 0.25, 0.25 0.25) …… ) • See more here: http://docs.geoserver.org/latest/en/user/styling/sld/exte nsions/pointsymbols.html Other mark options
25. Filling polygons 25
26. Solid filling * { fill: lightgrey; stroke-width: 0.5; } <sld:PolygonSymbolizer> <sld:Fill> <sld:CssParameter name="fill">#d3d3d3</sld:CssParameter> </sld:Fill> <sld:Stroke> <sld:CssParameter name="stroke-width">0.5</sld:CssParameter> </sld:Stroke> </sld:PolygonSymbolizer> SLD CSS
27. Solid fills and repeating images fill [@sd < 800k][type in ('cemetery', 'grave_yard')] { fill: #aacbaf; [@sd < 50k] { [religion = 'jewish'] { fill: #aacbaf, url('symbols/grave_yard_jewish.png'); }; [religion = 'christian'] { fill: #aacbaf, url('symbols/grave_yard_christian.png'); }; [religion = 'INT-generic'] { fill: #aacbaf, url('symbols/grave_yard_generic.png'); }; }; } CSS
28. Hatching <sld:PolygonSymbolizer> <sld:Fill> <sld:GraphicFill> <sld:Graphic> <sld:Mark> <sld:WellKnownName>shape://times</sld:WellKnownName> <sld:Stroke> <sld:CssParameter name="stroke">#ADD8E6</sld:CssParameter> </sld:Stroke> </sld:Mark> <sld:Size>8</sld:Size> </sld:Graphic> </sld:GraphicFill> </sld:Fill> </sld:PolygonSymbolizer> </sld:Rule> [@scale < 10000] { fill: symbol('shape://times'); fill-size: 8; :fill { stroke: #ADD8E6; } } SLD CSS
29. Filling Painting lines 29
30. Solid lines (OSM admin borders) [type = 'administrative'] { [admin_level <= 4], [admin_level = 5 or admin_level = 6][@sd <= 400k], [admin_level = 7 or admin_level = 8][@sd <= 200k], [admin_level = 9 or admin_level = 10][@sd <= 100k] { stroke: #ac46ac; stroke-opacity: 0.4; } } CSS
31. Dashes/Marks/images along a line * { stroke: darkRed, symbol('circle'); stroke-dasharray: 10 14, 6 18; stroke-dashoffset: 14, 0; :stroke { fill: darkRed; size: 6; } } • Two coordinated dashed lines • One made with lines • One made with circles • The offset shifts them to have one appear in the empty spaces of the other CSS
32. Labeling 32
33. Vendor options • Priority labelling, static or attribute based • Deluge of vendor options to control in detail labelling: • group • labelAllGroup • spaceAround • followLine • maxDisplacement • repeat • maxAngleDelta • autoWrap • forceLeftToRight • conflictResolution • goodnessOfFit • polygonAlign • graphic-resize • graphic-margin • partials • underlineText • strikethroughText • charSpacing • wordSpacing
34. Polygon labels <sld:TextSymbolizer> <sld:Label> <ogc:PropertyName>FULLNAME</ogc:PropertyName> </sld:Label> <sld:Font> <sld:CssParameter name="font-family">Arial</sld:CssParameter> <sld:CssParameter name="font-size">14.0</sld:CssParameter> <sld:CssParameter name="font-weight">bold</sld:CssParameter> </sld:Font> <sld:LabelPlacement> <sld:PointPlacement> <sld:AnchorPoint> <sld:AnchorPointX>0.5</sld:AnchorPointX> <sld:AnchorPointY>0.5</sld:AnchorPointY> </sld:AnchorPoint> </sld:PointPlacement> </sld:LabelPlacement> <sld:Fill> <sld:CssParameter name="fill">#000000</sld:CssParameter> </sld:Fill> <sld:Priority>50000</sld:Priority> <sld:VendorOption name="autoWrap">100</sld:VendorOption> <sld:VendorOption name="maxDisplacement">200</sld:VendorOption> <sld:VendorOption name="goodnessOfFit">0.9</sld:VendorOption> </sld:TextSymbolizer>
35. Point labels and obstacles [@sd < 200k] { label: [FULLNAME]; label-anchor: 0.5 1.0; label-offset: 0.0 -14.0; font-fill: #000033; font-family: Arial; font-size: 12; halo-color: white; halo-radius: 1.5; label-priority: 200000; label-auto-wrap: 100; mark: url('./img/landmarks/${IMAGE}’); mark-label-obstacle: true; } «FULLNAME» attribute Auto wrapping label with halo. Data driven symbol URL Labels won’t overlap the symbol CSS
36. Line labels [@sd < 200k] { label: [LABEL_NAME]; font-fill: #000000; font-family: Arial; font-size: 13; font-style: normal; font-weight: bold; halo-color: #FFFFFF; halo-radius: 1; label-follow-line: true; label-repeat: 400; label-group: true; label-max-displacement: 200; } Draw «LABEL_NAME», black, with white halo Draw them along lines, fuse segments with same label, repeat CSS
37. Raster styling 37
38. A DEM and a color map • SRTM from USGS • Standard color map • Also shaded relief (not shown in the css below) [@sd > 75000] { raster-channels: auto; raster-color-map: color-map-entry(#00BFBF, -100.0, 0) color-map-entry(#00FF00, 920.0, 0) color-map-entry(#00FF00, 920.0, 1.0) color-map-entry(#FFFF00, 1940.0, 1.0) color-map-entry(#FFFF00, 1940.0, 1.0) color-map-entry(#FF7F00, 2960.0, 1.0) color-map-entry(#FF7F00, 2960.0, 1.0) color-map-entry(#BF7F3F, 3980.0, 1.0) color-map-entry(#BF7F3F, 3980.0, 1.0) color-map-entry(#141514, 5000.0, 1.0); } CSS
39. Contrast enhancement http://docs.geoserver.org/latest/en/user/styling/sld-reference/rastersymbolizer. html#contrastenhancement <sld:RasterSymbolizer> <sld:ContrastEnhancement> <sld:Normalize> <sld:VendorOption name="algorithm"> StretchToMinimumMaximum </sld:VendorOption> <sld:VendorOption name="minValue">50</sld:VendorOption> <sld:VendorOption name="maxValue">800</sld:VendorOption> </sld:Normalize> </sld:ContrastEnhancement> </sld:RasterSymbolizer> GeoServer vendor extension SLD
40. Other assorted features 40
41. Color blending and alpha compositing multiply color-burn difference Source Destination https://docs.geoserver.org/latest/en/user/styling/sld/extensions/composite-blend/index.html More info at: Mask with alpha compositing <VendorOption name="composite"> multiply, 0.5 </VendorOption>
42. Z ordering http://docs.geoserver.org/latest/en/user/styling/sld- extensions/z-order/example.html [class = 'motorways'] { stroke: #990000, #ff6666; stroke-width: 8, 6; stroke-linecap: round; z-index: 0, 3; } [class = 'railways'] { stroke: #333333; stroke-width: 3; z-index: 2; } [class = 'railways'] { stroke: #ffffff; stroke-width: 1.5; stroke-dasharray: 5 5; z-index: 3; } * { sort-by: "z_order"; sort-by-group: "roadsGroup"; } CSS 42
43. Geometry transformations [@scale < 10000] { fill-geometry: [offset(the_geom, 6, -6)]; fill: darkgray; z-index: 0; } [@scale < 10000] { fill: #b3b3b3; z-index: 1; } CSS 43
44. Rendering transformations • WPS + WMS + rendering optimizations • In this slide, on the fly contour extraction * { transform: ras:Contour(levels: 1100 1200 1300 1400 1500 1600 1700 1800); stroke: black; label: [GRAY-INDEX]; font-fill: black; font-family: Sans; font-size: 12; halo-radius: 2; halo-color: white; label-follow-line: true } CSS 44
45. Jiffle map algebra * { transform: ras:Jiffle(script: ‘ nir = src[7]; vir = src[3]; dest = (nir-vir)/(nir+vir);’); raster-channels: auto; raster-color-map: color-map-entry(#00BFBF, -100.0, 0) color-map-entry(#00FF00, 920.0, 0) … } CSS
46. Legend control too (2.20.x) That “boundary” rule does help making the legend readable. Yet, we need borders and labels. Valid values: mapOnly, legendOnly <Rule> <Title>Boundary</ Title> <VendorOption name="inclusion" >mapOnly</VendorOption >
47. Point and click editors 47
48. QGIS SLD export • Basic vector and raster styling covered • Much advanced bits missing though • Needs sponsoring on both ends (QGIS and GeoServer)
49. GeoStyler (community module)
50. MapStore styler
51. That’s all folks! Questions? info@geosolutionsgroup.com 51