This is great, thanks for the info. I believe we will be working through the GUI to do the symbolization.
Thanks, Eric On Thu, Mar 4, 2021 at 8:50 AM Martin Dobias <wonder...@gmail.com> wrote: > Hi Eric > > I don't know about the S57 driver, best to ask on the gdal mailing list > about that... > > As for QML format... you should not try to read/write raw XML data of QML > files: although that happens rarely, the format may change between versions > of QGIS as the schema is not guaranteed to be stable and it should be > considered as an implementation detail of QGIS. To prepare QML files, the > two preferred ways are: > 1. GUI - use QGIS app to set up styling of the map layer > 2. Python API - use PyQGIS library to create renderer (e.g. > QgsSingleSymbolRenderer) and symbol (e.g. QgsMarkerSymbol) objects and > assign them to a map layer > Then to save the QML file, you can again either use GUI (layer properties > dialog) or use Python API (QgsMapLayer.saveNamedStyle(...)) > > Regards > Martin > > > On Wed, Mar 3, 2021 at 7:02 PM Eric Younkin - NOAA Federal < > eric.g.youn...@noaa.gov> wrote: > >> All, >> >> This is very useful, thanks. The S57 driver does appear to give the >> layers by names that I recognize: >> >> INFO: Open of `C:\collab\dasktest\data_dir\13238_FFF.000' >> using driver `S57' successful. >> 1: DSID (None) >> 2: LNDARE >> 3: LNDELV >> 4: SBDARE >> 5: UWTROC (Point) >> >> I've found the QML format spec here >> <https://docs.qgis.org/3.16/en/docs/user_manual/appendices/qgis_file_formats.html>, >> but is there any guidance on starting from scratch? Thanks again for all >> the help. >> >> Eric >> >> >> On Wed, Mar 3, 2021 at 12:38 PM Martin Dobias <wonder...@gmail.com> >> wrote: >> >>> Hi Eric >>> >>> On Wed, Mar 3, 2021 at 5:48 PM Eric Younkin - NOAA Federal < >>> eric.g.youn...@noaa.gov> wrote: >>> >>>> Thanks for the quick reply. This is for NOAA nautical chart symbology, >>>> following the s57/s52 spec. You can see the symbology in the online viewer >>>> here <https://www.nauticalcharts.noaa.gov/ENCOnline/enconline.html>. >>>> It is basically a very complex spec that we generated for display in a >>>> wxPython widget a long time ago using GDAL 1.x commands. S57 is already an >>>> existing OGR driver, although I do not know what exactly that driver does. >>>> I do know that it does not somehow generate the symbology of the data for >>>> you to then render. >>>> >>>> The vector data would be a combination of area/line/point features, and >>>> I don't think it would be a fit for the Mesh layer. >>>> >>>> We'd like to make this symbology available in QGIS, so that users can >>>> drag in a s57 file and view the chart. You can use one of our WMS >>>> services, but having the file support would be useful. Ideally in a plugin >>>> layer, so that I can also use it in our other apps that use PYQGIS >>>> QgsMapCanvas >>>> widgets. >>>> >>> >>> Thanks for more background. In this case the mesh layer indeed is not >>> useful. I have not worked with S57 before, but if there is OGR driver >>> available, it should be relatively easy to load and style the data without >>> a plugin layer. You do not need to rely on styling provided by OGR (if >>> provided at all). It looks like you only need to load the data as a bunch >>> of vector layers using OGR (one for each object type) and then apply >>> styling to those individual layers. Styling of vector layers in QGIS is >>> fairly strong, with features like rule-based rendering, data-defined >>> properties and geometry generators you can handle even very complex styles. >>> After preparing individual styles for vector layers, you can save them to >>> .qml files, and then your plugin would have just a simple task of taking >>> the input file(s), load layers and apply saved styles. >>> >>> I would resort to writing a custom plugin layer only when when all other >>> options fail - it is more complex, and generally the user experience is not >>> great. >>> >>> Regards >>> Martin >>> >>> >> >> -- >> Eric Younkin >> Physical Scientist >> NOAA OCS, Hydrographic Systems and Technology Branch >> 1315 East-West Highway >> N/CS11, Room 6604 >> Silver Spring, MD 20910 >> Office: 240-847-8208 >> Cell: 828-331-8197 >> > -- Eric Younkin Physical Scientist NOAA OCS, Hydrographic Systems and Technology Branch 1315 East-West Highway N/CS11, Room 6604 Silver Spring, MD 20910 Office: 240-847-8208 Cell: 828-331-8197
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