Book Image

Building Mapping Applications with QGIS

By : Erik Westra
Book Image

Building Mapping Applications with QGIS

By: Erik Westra

Overview of this book

Table of Contents (16 chapters)
Building Mapping Applications with QGIS
About the Author
About the Reviewers
Free Chapter
Getting Started with QGIS

Combining symbol layers

By combining symbol layers, you can achieve a range of complex visual effects. For example, you can combine an instance of QgsSimpleMarkerSymbolLayerV2 with an instance of QgsVectorFieldSymbolLayer to display a point geometry using two symbols at once:

One of the main uses of symbol layers is to draw different LineString or PolyLine symbols to represent different types of roads. For example, you can draw a complex road symbol by combining multiple symbol layers, like this:

This effect is achieved by using three separate symbol layers:

Here is the Python code used to generate the preceding map symbol:

symbol =QgsLineSymbolV2.createSimple({})
symbol.deleteSymbolLayer(0) # Remove default symbol layer.

symbol_layer = QgsSimpleLineSymbolLayerV2()
symbol_layer.setColor(QColor("light gray"))

symbol_layer = QgsSimpleLineSymbolLayerV2()