[gdal-dev] GDAL / LIBKML / XLSX Layer Style

[Adam Jamison]

GDAL Guru's,

I'm looking at how to apply some sort of predefined style to a dataset coming from XLSX and going to KML (LIBKML).

My thoughts are XLSX --> VRT --> KML.

I can successfully add OGR_STYLE at each feature and style the features individually, however I'm hoping I can leverage existing styles at the layer / folder level of the KML. (https://gdal.org/drivers/vector/libkml.html#styletable, https://gdal.org/drivers/vector/libkml.html#style)

For the KML file specifically I'd love to be able to append a StyleURL in the format 'sharedstyle.kml#Zone' and somehow bundle the ogr2ogr generated file with this sharedstyle.kml in a kmz...?

Some data sets:

The XLSX data:
ElementId
Name
WKT
1179
Zone1
POLYGON ((530494.56 6944864.63, 530486.431754 6944883.227494, 530497.919033 6944897.30242, 530575.4 6944931.94, 530589.075307 6944920.363282, 530608.620897 6944914.005078, 530494.56 6944864.63))
1180
Zone4
POLYGON ((530640.737164 6944927.90768, 530633.256 6944960.922, 530648.673025 6944964.552847, 530660.54 6944936.48, 530640.737164 6944927.90768))
1181
Zone2
POLYGON ((530494.56 6944864.63, 530501.34 6944857.63, 530665.986727 6944919.946257, 530660.54 6944936.48, 530494.56 6944864.63))


The VRT file (Local.vrt):
<OGRVRTDataSource>
  <OGRVRTLayer name="Zone">
    <SrcDataSource relativeToVRT="1">Local.xlsx</SrcDataSource>
    <FID name="ElementId"/>
    <OpenOptions>
      <OOI key="HEADERS">FORCE</OOI>
    </OpenOptions>
    <SrcSQL>Select ElementId, Name, WKT, '@Zone' as OGR_STYLE from Zone</SrcSQL>
    <GeometryType>wkbPolygon</GeometryType>
    <LayerSRS>EPSG:28356</LayerSRS>
    <GeometryField encoding="WKT" name="Geometry" field="WKT" reportSrcColumn="FALSE" />
    <Field name="ElementId" type="Integer" />
    <Field name="Name" type="String" />
    <Style>OGR_STYLE</Style>
  </OGRVRTLayer>
</OGRVRTDataSource>

Template KML file (Base.kml):
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns=http://www.opengis.net/kml/2.2>
  <Document id="root_doc">
    <Style id="Zone">
      <LineStyle>
        <color>ff0000ff</color>
        <width>15</width>
      </LineStyle>
      <PolyStyle>
        <color>7f7faaaa</color>
        <colorMode>random</colorMode>
      </PolyStyle>
    </Style>
  </Document>
</kml>

Local.ofs:
#OFS-Version: 1.0
#StyleField: "LayerStyle"

DefaultStyle: BRUSH(fc:#000000);PEN(c:#000000)
Zone:      BRUSH(fc:#0000FF);PEN(c:#000000)

ogr2ogr Local.kml Local.vrt Zone -oo HEADERS=FORCE -t_srs EPSG:4326 -f LIBKML -lco FOLDER=NO

How do I append layer level rules to a KML file when using ogr2ogr, things I've tried:
'BRUSH(fc:#0000FF);PEN(c:#000000)', writes a style element to each feature (this will work but not ideal).
'@Zone', generates '#Zone' in the styleurl, but I don't know how to append the style rule to the newly created kml file.
'@styles.kml#Zome', generates '#styles.kml#Zone', just not going to cut it.

https://gdal.org/user/ogr_feature_style.html#styles-table-format
I've tinkered with the .ofs file, documentation on this is a little sparse not sure exactly what to do with it?



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