QGIS Python Programming Cookbook电子书

QGIS Python Programming Cookbook

Table of Contents

QGIS Python Programming Cookbook

Credits

About the Author

About the Reviewers

www.PacktPub.com

Support files, eBooks, discount offers, and more

Why Subscribe?

Free Access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Sections

Getting ready

How to do it…

How it works…

There's more…

See also

Conventions

Reader feedback

Customer support

Downloading the example code

Downloading the color images of this book

Errata

Piracy

Questions

1. Automating QGIS

Introduction

Installing QGIS for development

Getting ready

How to do it

Installing PyQGIS using the Debian package manager

Installing PyQGIS using the RPM package manager

Setting the environment variables

Setting the environment variables on Windows

Setting the environment variables on Linux

How it works…

There's more…

Finding the PyQGIS path on Windows

Finding the location of the QGIS Python installation on other platforms

Using the QGIS Python console for interactive control

How to do it…

How it works…

Using the Python ScriptRunner plugin

Getting ready

How to do it…

How it works…

Setting up your QGIS IDE

Getting ready

How to do it…

Adding the QGIS Python interpreter on Windows

Adding the PyQGIS module paths to the interpreter

Adding the PyQGIS API to the IDE

Adding environment variables

How it works…

Debugging QGIS Python scripts

How to do it…

Configuring QGIS

Configuring Eclipse

Testing the debugger

How it works…

Navigating the PyQGIS API

Getting ready

How to do it…

How it works…

There's more…

Creating a QGIS plugin

Getting ready

How to do it…

How it works…

There's more…

Distributing a plugin

Getting ready

How to do it…

How it works…

Creating a standalone application

Getting ready

How to do it…

How it works…

There's more...

Storing and reading global preferences

Getting ready

How to do it…

How it works…

There's more…

Storing and reading project preferences

Getting ready

How to do it…

How it works…

There's more…

Accessing the script path from within your script

Getting ready

How to do it…

How it works…

There's more…

2. Querying Vector Data

Introduction

Loading a vector layer from a file sample

Getting ready

How to do it...

How it works...

Loading a vector layer from a spatial database

Getting ready

How to do it...

How it works...

Examining vector layer features

Getting ready

How to do it...

How it works...

Examining vector layer attributes

Getting ready

How to do it...

How it works...

There's more...

Filtering a layer by geometry

Getting ready

How to do it...

How it works...

Filtering a layer by attributes

Getting ready

How to do it...

How it works...

Buffering a feature intermediate

Getting ready

How to do it...

How it works...

Measuring the distance between two points

Getting ready

How to do it...

How it works...

Measuring the distance along a line sample

Getting ready

How to do it...

How it works...

Calculating the area of a polygon

Getting ready

How to do it...

How it works...

Creating a spatial index

Getting ready

How to do it...

How it works...

Calculating the bearing of a line

Getting ready

How to do it...

How it works...

Loading data from a spreadsheet

Getting ready

How to do it...

How it works...

There's more...

3. Editing Vector Data

Introduction

Creating a vector layer in memory

Getting ready

How to do it...

How it works...

There's more…

Adding a point feature to a vector layer

Getting ready

How to do it...

How it works...

Adding a line feature to a vector layer

Getting ready

How to do it...

How it works...

Adding a polygon feature to a vector layer

Getting ready

How to do it...

How it works...

Adding a set of attributes to a vector layer

Getting ready

How to do it...

How it works...

Adding a field to a vector layer

Getting ready

How to do it...

How it works...

Joining a shapefile attribute table to a CSV file

Getting ready

How to do it...

How it works...

There's more...

Moving vector layer geometry

Getting ready

How to do it...

How it works...

Changing a vector layer feature's attribute

Getting ready

How to do it...

How it works...

Deleting a vector layer feature

Getting ready

How to do it...

How it works...

Deleting a vector layer attribute

Getting ready

How to do it...

How it works...

Reprojecting a vector layer

Getting ready

How to do it...

How it works...

Converting a shapefile to KML

Getting ready

How to do it...

How it works...

Merging shapefiles

Getting ready

How to do it...

How it works...

There's more...

Splitting a shapefile

Getting ready

How to do it...

How it works...

Generalizing a vector layer

Getting ready

How to do it...

How it works...

Dissolving vector shapes

Getting ready

How to do it...

How it works...

Performing a union on vector shapes

Getting ready

How to do it...

How it works...

Rasterizing a vector layer

Getting ready

How to do it...

How it works...

4. Using Raster Data

Introduction

Loading a raster layer

Getting ready

How to do it...

How it works...

Getting the cell size of a raster layer

Getting ready

How to do it...

How it works...

Obtaining the width and height of a raster

Getting ready

How to do it...

How it works...

Counting raster bands

Getting ready

How to do it...

How it works...

Swapping raster bands

Getting ready

How to do it...

How it works...

There's more...

Querying the value of a raster at a specified point

Getting ready

How to do it...

How it works...

Reprojecting a raster

Getting ready

How to do it...

How it works...

There's more...

Creating an elevation hillshade

Getting ready

How to do it...

How it works...

Creating vector contours from elevation data

Getting ready

How to do it...

How it works...

Sampling a raster dataset using a regular grid

Getting ready

How to do it...

How it works...

There's more...

Adding elevation data to line vertices using a digital elevation model

Getting ready

How to do it...

How it works...

There's more...

Creating a common extent for rasters

Getting ready

How to do it...

How it works...

Resampling raster resolution

Getting ready

How to do it...

How it works...

Counting the unique values in a raster

Getting ready

How to do it...

How it works...

Mosaicing rasters

Getting ready

How to do it...

How it works...

Converting a TIFF image to a JPEG image

Getting ready

How to do it...

How it works...

Creating pyramids for a raster

Getting ready

How to do it...

How it works...

Converting a pixel location to a map coordinate

Getting ready

How to do it...

How it works...

Converting a map coordinate to a pixel location

Getting ready

How to do it...

How it works...

Creating a KML image overlay for a raster

Getting ready

How to do it...

How it works...

There's more...

Classifying a raster

Getting ready

How to do it...

How it works...

Converting a raster to a vector

Getting ready

How to do it...

How it works...

Georeferencing a raster from control points

Getting ready

How to do it...

How it works...

Clipping a raster using a shapefile

Getting ready

How to do it...

How it works...

5. Creating Dynamic Maps

Introduction

Accessing the map canvas

Getting ready

How to do it...

How it works...

Changing the map units

Getting ready

How to do it...

How it works...

Iterating over layers

Getting ready

How to do it...

How it works...

Symbolizing a vector layer

Getting ready

How to do it...

How it works...

Rendering a single band raster using a color ramp algorithm

Getting ready

How to do it...

How it works…

Creating a complex vector layer symbol

Getting ready

How to do it…

How it works…

Using icons as vector layer symbols

Getting ready

How to do it…

How it works…

Creating a graduated vector layer symbol renderer

Getting ready

How to do it...

How it works...

Creating a categorized vector layer symbol

Getting ready

How to do it...

How it works...

Creating a map bookmark

Getting ready

How to do it...

How it works...

Navigating to a map bookmark

Getting ready

How to do it...

How it works...

Setting scale-based visibility for a layer

Getting ready

How to do it...

How it works...

Using SVG for layer symbols

Getting ready

How to do it...

How it works...

Using pie charts for symbols

Getting ready

How to do it...

How it works...

There's more...

Using the OpenStreetMap service

Getting ready

How to do it...

How it works...

Using the Bing aerial image service

Getting ready

How to do it...

How it works...

Adding real-time weather data from OpenWeatherMap

Getting ready

How to do it...

How it works...

Labeling features

Getting ready

How to do it...

How it works...

Changing map layer transparency

Getting ready

How to do it...

How it works...

Adding standard map tools to the canvas

Getting ready

How to do it...

How it works...

Using a map tool to draw points on the canvas

Getting ready

How to do it...

How it works...

Using a map tool to draw polygons or lines on the canvas

Getting ready

How to do it...

How it works...

Building a custom selection tool

Getting ready

How to do it...

How it works...

Creating a mouse coordinate tracking tool

Getting ready

How to do it...

How it works...

6. Composing Static Maps

Introduction

Creating the simplest map renderer

Getting ready

How to do it...

How it works...

There's more...

Using the map composer

Getting ready

How to do it...

How it works...

There's more…

Adding labels to a map for printing

Getting ready

How to do it...

How it works...

Adding a scale bar to the map

Getting ready

How to do it...

How it works...

Adding a north arrow to the map

Getting ready

How to do it...

How it works...

There's more...

Adding a logo to the map

Getting ready

How to do it...

How it works...

Adding a legend to the map

Getting ready

How to do it...

How it works...

Adding a custom shape to the map

Getting ready

How to do it...

How it works...

There's more...

Adding a grid to the map

Getting ready

How to do it...

How it works...

Adding a table to the map

Getting ready

How to do it...

How it works...

Adding a world file to a map image

Getting ready

How to do it...

How it works...

Saving a map to a project

Getting ready

How to do it...

How it works...

Loading a map from a project

Getting ready

How to do it...

How it works...

7. Interacting with the User

Introduction

Using log files

Getting ready

How to do it...

How it works...

Creating a simple message dialog

Getting ready

How to do it...

How it works...

There's more…

Creating a warning dialog

Getting ready

How to do it...

How it works...

Creating an error dialog

Getting ready

How to do it...

How it works...

Displaying a progress bar

Getting ready

How to do it...

How it works...

There's more…

Creating a simple text input dialog

Getting ready

How to do it...

How it works...

Creating a file input dialog

Getting ready

How to do it...

How it works...

There's more…

Creating a combobox

Getting ready

How to do it...

How it works...

Creating radio buttons

Getting ready

How to do it...

How it works...

Creating checkboxes

Getting ready

How to do it...

How it works...

Creating tabs

Getting ready

How to do it...

How it works...

Stepping the user through a wizard

Getting ready

How to do it...

How it works...

Keeping dialogs on top

Getting ready

How to do it...

How it works...

8. QGIS Workflows

Introduction

Creating an NDVI

Getting ready

How to do it...

How it works...

Geocoding addresses

Getting ready

How to do it...

How it works...

There's more...

Creating raster footprints

Getting ready

How to do it...

How it works...

There's more...

Performing network analysis

Getting ready

How to do it...

How it works...

Routing along streets

Getting ready

How to do it...

How it works...

Tracking a GPS

Getting ready

How to do it...

How it works...

There's more...

Creating a mapbook

Getting ready

How to do it...

How it works...

Finding the least cost path

Getting ready

How to do it...

How it works...

Performing nearest neighbor analysis

Getting ready

How to do it...

How it works...

Creating a heat map

Getting ready

How to do it...

How it works...

There's more...

Creating a dot density map

Getting ready

How to do it...

How it works...

Collecting field data

Getting ready

How to do it...

How it works...

Computing road slope using elevation data

Getting ready

How to do it...

How it works...

Geolocating photos on the map

Getting ready

How to do it...

How it works...

There's more...

Image change detection

Getting ready

How to do it...

How it works...

9. Other Tips and Tricks

Introduction

Creating tiles from a QGIS map

Getting ready

How to do it...

How it works...

Adding a layer to geojson.io

Getting ready

How to do it...

How it works...

There's more...

Rendering map layers based on rules

Getting ready

How to do it...

How it works...

Creating a layer style file

Getting ready

How to do it...

How it works...

Using NULL values in PyQGIS

Getting ready

How to do it...

How it works...

Using generators for layer queries

Getting ready

How to do it...

How it works...

Using alpha values to show data density

Getting ready

How to do it...

How it works...

Using the __geo_interface__ protocol

Getting ready

How to do it...

How it works...

Generating points along a line

Getting ready

How to do it...

How it works...

There's more...

Using expression-based labels

Getting ready

How to do it...

How it works...

Creating dynamic forms in QGIS

Getting ready

How to do it...

How it works...

Calculating length for all selected lines

Getting ready

How to do it...

How it works...

Using a different status bar CRS than the map

Getting ready

How to do it...

How it works...

Creating HTML labels in QGIS

Getting ready

How to do it...

How it works...

There's more...

Using OpenStreetMap's points of interest in QGIS

Getting ready

How to do it...

How it works...

Visualizing data in 3D with WebGL

Getting ready

How to do it...

How it works...

Visualizing data on a globe

Getting ready

How to do it...

How it works...

Index