Map layer transparency allows you to change the opacity of a layer, so the items behind it are visible to some degree. A common technique is to make a vector layer polygon partially transparent in order to allow the underlying imagery or elevation data to add texture to the data.
In a directory called ms
, in your qgis_data
directory, download and extract the following shapefile from
https://geospatialpython.googlecode.com/files/Mississippi.zip.
The process is extremely simple. Transparency is just a method:
lyr = QgsVectorLayer("/Users/joellawhead/qgis_data/ms/mississippi.shp", "Mississippi", "ogr")
50
percent:lyr.setLayerTransparency(50)
QgsMapLayerRegistry.instance().addMapLayer(lyr)