Creating stunning maps with GeoServer With SLD and CSS Ing. Andrea Aime GeoSolutions 1 

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 

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 

Quick tour of styling languages 4 

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 

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 

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 

SLD 1.0 example … type alpine_hut 100000.0 image/png Filter Scale dep. Symbolizer 

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 

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 

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 

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 

What’s next ● Going to explore styling concepts ● Languages used in examples ● SLD 1.0 + GS extensions ● GeoCSS SLD CSS 

Scale dependencies 14 

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 

Expressing scale dependency filters ● SLD: ● 1000 ● 1000000 ● CSS ● [@sd > 1k][@sd < 1M] Compact expression of large numbers makes them readable at a glance, e.g., 100k, 1M , 10M 

Unit of Measure ● Useful if you have real world measures of line thicknesses and the like … #0000FF 5 ... … stroke: blue; stroke-width: 5m; SLD CSS 

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 

Transformation functions in SLD #e66e89 wms_scale_denominator 2 400000 1.9 800000 1.4 1500000 1 3000000 0.8 6000000 0.5 SLD 

Point styling 20 

Simple image [type = 'alpine_hut'][@sd < 100k] { mark: url('symbols/alpinehut.p.16.png'); } type alpine_hut 100000.0 image/png SLD CSS 

Marks (SVG in this case) [type = 'bank'][@sd < 6k] { mark: symbol('file://symbols/bank.svg'); :mark { fill: #734a08 }; mark-size: 14; } type bank 6000 file://symbols/bank.svg #734a08 14 CSS bank.svg 

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 

● Many other options! ● Built-in symbol names (well known marks): circle, square, triangle, … ● From TTF fonts using the name ttf://#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 

Filling polygons 25 

Solid filling * { fill: lightgrey; stroke-width: 0.5; } #d3d3d3 0.5 SLD CSS 

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 

Hatching shape://times #ADD8E6 8 [@scale < 10000] { fill: symbol('shape://times'); fill-size: 8; :fill { stroke: #ADD8E6; } } SLD CSS 

Filling Painting lines 29 

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 

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 

Labeling 32 

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 

Polygon labels FULLNAME Arial 14.0 bold 0.5 0.5 #000000 50000 100 200 0.9 

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 

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 

Raster styling 37 

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 

Contrast enhancement http://docs.geoserver.org/latest/en/user/styling/sld-reference/rastersymbolizer. html#contrastenhancement StretchToMinimumMaximum 50 800 GeoServer vendor extension SLD 

Other assorted features 40 

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 multiply, 0.5 

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 

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 

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 

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 

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 Boundary</ Title> <VendorOption name="inclusion" >mapOnly</VendorOption > 

Point and click editors 47 

QGIS SLD export • Basic vector and raster styling covered • Much advanced bits missing though • Needs sponsoring on both ends (QGIS and GeoServer) 

GeoStyler (community module) 

MapStore styler 

That’s all folks! Questions? [email protected] 51