QGIS Python Programming Cookbook

Cover......Page 1
Copyright......Page 3
Credits......Page 4
About the Author......Page 5
About the Reviewers......Page 6
www.PacktPub.com......Page 9
Table of Contents......Page 10
Preface......Page 16
 Introduction......Page 22
 Installing QGIS for development......Page 23
 Using the QGIS Python console for interactive control......Page 26
 Using the Python ScriptRunner plugin......Page 27
 Setting up your QGIS IDE......Page 29
 Debugging QGIS Python scripts......Page 34
 Navigating the PyQGIS API......Page 38
 Creating a QGIS plugin......Page 40
 Distributing a plugin......Page 43
 Creating a standalone application......Page 46
 Storing and reading global preferences......Page 48
 Storing and reading project preferences......Page 49
 Accessing the script path from within your script......Page 51
 Introduction......Page 52
 Loading a vector layer from a file sample......Page 53
 Loading a vector layer from a spatial database......Page 55
 Examining vector layer features......Page 57
 Examining vector layer attributes......Page 58
 Filtering a Layer by geometry......Page 59
 Filtering a layer by attributes......Page 61
 Buffering a feature intermediate......Page 63
 Measuring the distance between two points......Page 65
 Measuring the distance along a line sample......Page 66
 Calculating the area of a polygon......Page 68
 Creating a spatial index......Page 69
 Calculating the bearing of a line......Page 70
 Loading data from a spreadsheet......Page 72
Chapter 3: Editing Vector Data......Page 76
 Creating a vector layer in memory......Page 77
 Adding a point feature to a vector layer......Page 78
 Adding a line feature to a vector layer......Page 80
 Adding a polygon feature to a vector layer......Page 81
 Adding a set of attributes to a vector layer......Page 83
 Adding a field to a vector layer......Page 84
 Join ing a shapefile attribute table to a CSV File......Page 86
 Moving vector layer geometry......Page 88
 Changing a vector layer feature's attribute......Page 89
 Deleting a vector layer feature......Page 91
 Deleting a vector layer attribute......Page 92
 Reprojecting a vector layer......Page 93
 Converting a shapefile to KML......Page 94
 Merging shapefiles......Page 95
 Splitting a shapefile......Page 96
 Generalizing a vector layer......Page 97
 Dissolving vector shapes......Page 99
 Performing a union on vector shapes......Page 101
 Rasterizing a vector layer......Page 103
Chapter 4: Using Raster Data......Page 106
 Introduction......Page 107
 Loading a raster layer......Page 108
 Getting the cell size of a raster layer......Page 110
 Obtaining the width and height of a raster......Page 111
 Counting raster bands......Page 112
 Swapping raster bands......Page 113
 Querying the value of a raster at a specified point......Page 114
 Reprojecting a raster......Page 115
 Creating an elevation hillshade......Page 117
 Creating vector contours from elevation data......Page 119
 Sampling a raster dataset using a regular grid......Page 121
 Adding elevation data to line vertices using a digital elevation model......Page 125
 Creating a common extent for rasters......Page 127
 Resampling raster resolution......Page 129
 Counting the unique values in a raster......Page 131
 Mosaicing rasters......Page 132
 Converting a TIFF image to a JPEG image......Page 133
 Creating pyramids for a raster......Page 134
 Converting a pixel location to a map coordinate......Page 135
 Converting a map coordinate to a pixel location......Page 137
 Creating a KML image overlay for a raster......Page 138
 Classifying a raster......Page 142
 Converting a raster to a vector......Page 143
 Georeferencing a raster from control points......Page 145
 Clipping a raster using a shapefile......Page 147
Chapter 5: Creating Dynamic Maps......Page 150
 Accessing the map canvas......Page 151
 Changing the map units......Page 152
 Iterating over layers......Page 153
 Symbolizing a vector layer......Page 154
 Rendering a single band raster using a color ramp algorithm......Page 156
 Creating a complex vector layer symbol......Page 158
 Using icons as vector layer symbols......Page 160
 Creating a graduated vector layer symbol renderer......Page 162
 Creating a categorized vector layer symbol......Page 163
 Creating a map bookmark......Page 165
 Navigating to a map bookmark......Page 167
 Setting scale-based visibility for a layer......Page 168
 Using SVG for layer symbols......Page 169
 Using pie charts for symbols......Page 171
 Using the OpenStreetMap service......Page 175
 Using the Bing aerial image service......Page 176
 Adding real-time weather data from OpenWeatherMap......Page 178
 Labeling features......Page 179
 Changing map layer transparency......Page 180
 Adding standard map tools to the canvas......Page 181
 Using a map tool to draw points on the canvas......Page 184
 Using a map tool to draw polygons or lines on the canvas......Page 186
 Building a custom selection tool......Page 189
 Creating a mouse coordinate tracking tool......Page 192
 Introduction......Page 194
 Creating the simplest map renderer......Page 195
 Using the map composer......Page 197
 Adding labels to a map for printing......Page 200
 Adding a scale bar to the map......Page 202
 Adding a north arrow to the map......Page 204
 Adding a logo to the map......Page 207
 Adding a legend to the map......Page 209
 Adding a custom shape to the map......Page 210
 Adding a grid to the map......Page 214
 Adding a table to the map......Page 216
 Adding a world file to a map image......Page 218
 Saving a map to a project......Page 220
 Loading a map from a project......Page 221
Chapter 7: Interacting with the User......Page 222
 Using log files......Page 223
 Creating a simple message dialog......Page 224
 Creating a warning dialog......Page 225
 Creating an error dialog......Page 226
 Displaying a progress bar......Page 227
 Creating a simple text input dialog......Page 229
 Creating file input dialog......Page 230
 Creating a combobox......Page 232
 Creating radio buttons......Page 233
 Creating checkboxes......Page 235
 Creating tabs......Page 237
 Stepping the user through a wizard......Page 239
 Keeping dialogs on top......Page 242
Chapter 8: QGIS Workflows......Page 244
 Creating an NDVI......Page 245
 Geocoding addresses......Page 248
 Creating raster footprints......Page 250
 Performing network analysis......Page 254
 Routing along streets......Page 257
 Tracking a GPS......Page 259
 Creating a mapbook......Page 263
 Finding the least cost path......Page 266
 Performing nearest neighbor analysis......Page 268
 Creating a heat map......Page 270
 Creating a dot density map......Page 274
 Collecting field data......Page 276
 Computing road slope using elevation data......Page 279
 Geolocating photos on the map......Page 283
 Image change detection......Page 287
Chapter 9: Other Tips and Tricks......Page 290
 Creating tiles from a QGIS map......Page 291
 Adding a layer to geojson.io......Page 295
 Rendering map layers based on rules......Page 297
 Creating a layer style file......Page 301
 Using NULL values in PyQGIS......Page 303
 Using generators for layer queries......Page 304
 Using alpha values to show data density......Page 305
 Using the __geo_interface__ protocol......Page 309
 Generating points along a line......Page 310
 Using expression-based labels......Page 312
 Creating dynamic forms in QGIS......Page 313
 Calculating length for all selected lines......Page 316
 Using a different status bar CRS than the map......Page 317
 Creating HTML labels in QGIS......Page 318
 Using OpenStreetMap's points of interest in QGIS......Page 321
 Visualizing data in 3D with WebGL......Page 323
 Visualizing data on a globe......Page 326
Index......Page 330