No objections, great to have a useful solution. Is the opacity of the background color also defined?
Out of curiosity why as part of a single UserStyle, since an SLD may have several? Would it make sense to provide a background color as part of StyledLayerDescriptor which describes an entire map with several layers? On Wed, Sep 11, 2019 at 10:23 AM Andrea Aime <andrea.a...@geo-solutions.it> wrote: > Hi, > in Testbed 15 we are asked to implement a way to set the map background > color in the > style itself, at least for styles that are meant to be used as basemaps. > > The SLD specification does not allow for that, which makes sense in the > context of "overlay" WMS, > with a client deciding the set of layers to be displayed, and controlling > the background color from the > GetMap itself. > > However, the need to set the background color is real and we have seen in > GeoServer since the > beginning: anyone forgot about the "giant_polygon" layer used in the NYC > demo layer group? :-D > Looking at the MBStyles code I see a similar solution, the code is taking > the bgcolor specification > found in Mapbox GL and turning it into a inline user style with a GML > giant polygon defined inside. > > The giant polygon approach has been labelled as clumsy and ineffective, > and indeed, I have to agree: > > - Why expose a dedicated, user visible layer with a massive polygon > just to set the color of the painting canvas > - Reprojection issues abund when going to local projections, the > advanced projection handling help here by cutting the geometry, but it's > not available for all projections > > The idea proposed in the testbed is to add a BGColor element inside > UserStyle that would allow setting the background > color for the entire style (imagine a multi-layer stylesheet, also known > as style group, in GeoServer): > > <UserStyle> > <BGColor>FFAA00</BGColor> > ... > </UserStyle> > > The idea seems useful and has no backwards compatibility issues, so I'd > like to implement it, at least in the > SLD parser, to give a simple solution to.. well... a simple problem. > The renderer would then simply use the information to paint the canvas > with the first bgcolor found in the layer stack. > If the map is requested to be transparent (&transparent=true) then it > would ignore the bgcolor, allowing the layers > to be used both as suitable backgrounds but also as overlays > > Objections? :) > > Cheers > Andrea > > == GeoServer Professional Services from the experts! Visit > http://goo.gl/it488V for more information. == Ing. Andrea Aime @geowolf > Technical Lead GeoSolutions S.A.S. Via di Montramito 3/A 55054 Massarosa > <https://www.google.com/maps/search/Via+di+Montramito+3%2FA%0D%0A55054++Massarosa?entry=gmail&source=g> > (LU) phone: +39 0584 962313 fax: +39 0584 1660272 mob: +39 339 8844549 > http://www.geo-solutions.it http://twitter.com/geosolutions_it > ------------------------------------------------------- *Con riferimento > alla normativa sul trattamento dei dati personali (Reg. UE 2016/679 - > Regolamento generale sulla protezione dei dati “GDPR”), si precisa che ogni > circostanza inerente alla presente email (il suo contenuto, gli eventuali > allegati, etc.) è un dato la cui conoscenza è riservata al/i solo/i > destinatario/i indicati dallo scrivente. Se il messaggio Le è giunto per > errore, è tenuta/o a cancellarlo, ogni altra operazione è illecita. Le > sarei comunque grato se potesse darmene notizia. This email is intended > only for the person or entity to which it is addressed and may contain > information that is privileged, confidential or otherwise protected from > disclosure. We remind that - as provided by European Regulation 2016/679 > “GDPR” - copying, dissemination or use of this e-mail or the information > herein by anyone other than the intended recipient is prohibited. If you > have received this email by mistake, please notify us immediately by > telephone or e-mail.* > _______________________________________________ > GeoTools-Devel mailing list > GeoTools-Devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/geotools-devel > -- -- Jody Garnett
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