[GIS] How to export shapefile to SVG format using PyQGIS

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I am doing a project where I have to export file from shapefile to SVG format using PyQGIS.

I have read some articles regarding SimpleSvg plugin but I don't know how can we achieve the same task using PyQGIS.

Best Answer

SimpleSVG is a Python plugin https://plugins.qgis.org/plugins/simplesvg/ --> using PyQGIS!

Therefore its source code should be the perfect example of how to export SVG from QGIS.

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[GIS] Export shapefile From PostGIS

Just install GDAL and run it from Bash / terminal.

ogr2ogr -f "ESRI Shapefile" mydata.shp PG:"host=myhost user=myloginname dbname=mydbname password=mypassword" "mytable"

Or do not even bother with GDAL and just use something like below in terminal.

# pgsql2shp -f myfile -p 5555 my_db roads_table

[GIS] How to access shapefile m-values with pyqgis

Assuming you have a QgsGeometry object (eg the geometry returned when calling QgsFeature.geometry()), you can access it's raw geometry info by calling QgsGeometry.geometry() in QGIS 2.x or QgsGeometry.constGet() in QGIS 3 respectively. This returns the relevant QgsAbstractGeometry subclass for the geometry type. These subclasses have methods for reading points from the geometry as QgsPointV2 objects (QgsPoint in QGIS 3), which you can then directly retrieve the z or m values from. Sometimes (as is the case with QgsLineStringV2 you can even directly access the z/m values from the subclass itself.

Here's an example for QGIS 2.x:

g = feature.geometry()
line = g.geometry() #line returns a QgsLineStringV2 object
m = line.mAt(0) # m value of first vertex
z = line.zAt(0) # z value of first vertex

And another example for QGIS 3:

g = feature.geometry()
line = g.constGet() #line returns a QgsLineString object
m = line.mAt(0) # m value of first vertex
z = line.zAt(0) # z value of first vertex

An important thing to note is that only very recent gdal versions support m values, and older versions read in m values as z values. This will affect your results if using a file based format (eg shapefiles) in QGIS.

Best Answer

Related Solutions

[GIS] Export shapefile From PostGIS

[GIS] How to access shapefile m-values with pyqgis

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