QGIS/python/plugins/fTools/tools/ftools_utils.py

# Utility functions
# -------------------------------------------------
#
# combineVectorAttributes( QgsAttributeMap, QgsAttributeMap )
# convertFieldNameType( QgsField.name() )
# combineVectorFields( QgsVectorLayer, QgsVectorLayer )
# checkCRSCompatibility( QgsCoordinateReferenceSystem, QgsCoordinateReferenceSystem )
# writeVectorLayerToShape(QgsVectorLayer, QString *file path, QString *encoding style )
# getVectorTypeAsString( QgsVectorLayer )
# measurePerimeter( QgsGeometry )
# extractPoints( QgsGeometry )
# testForUniqueness( QList *QgsField, QList *QgsField )
# createUniqueFieldName( QgsField.name() )
# getLayerNames( QGis.vectorType() )
# getFieldNames( QgsVectorLayer )
# getVectorLayerByName( QgsVectorLayer.name() )
# getFieldList( QgsVectorLayer )
# createIndex( QgsVectorDataProvider )
# addShapeToCanvas( QString *file path )
# getUniqueValues( QgsVectorDataProvider, int *field id )
# saveDialog( QWidget *parent )
#
# -------------------------------------------------

from PyQt4.QtCore import *
from PyQt4.QtGui import *
from qgis.core import *
from qgis.gui import *

# From two input attribute maps, create single attribute map
def combineVectorAttributes( atMapA, atMapB ):
	attribA = atMapA.values()
	lengthA = len(attribA)
	attribB = atMapB.values()
	lengthB = len(attribB)
	attribA.extend( attribB )
	return dict( zip( range( 0, lengthB + lengthA ), attribA ) )

# For use with memory provider/layer, converts full field type to simple string
def convertFieldNameType( inName ):
	if inName == "Integer":
		return "int"
	elif inName == "Real":
		return "double"
	else:
		return "string"

# From two input field maps, create single field map
def combineVectorFields( layerA, layerB ):
	fieldsA = layerA.dataProvider().fields().values()
	fieldsB = layerB.dataProvider().fields().values()
	fieldsB = testForUniqueness( fieldsA, fieldsB )
	seq = range( 0, len( fieldsA ) + len( fieldsB ) )
	fieldsA.extend( fieldsB )
	fieldsA = dict( zip ( seq, fieldsA ) )
	return fieldsA

# Check if two input CRSs are identical
def checkCRSCompatibility( crsA, crsB ):
	if crsA == crsB:
		return True
	else:
		return False

# Convenience function to write vector layer to shapefile
def writeVectorLayerToShape( vlayer, outputPath, encoding ):
	mCodec = QTextCodec.codecForName( QString(encoding).toLocal8Bit().data() )
	if not mCodec:
		return False
	#Here we should check that the output path is valid
	QgsVectorFileWriter.writeAsShapefile( vlayer, outputPath, encoding, vlayer.dataProvider().crs(), False )
	return True

# For use with memory provider/layer, converts QGis vector type definition to simple string
def getVectorTypeAsString( vlayer ):
	if vlayer.geometryType() == QGis.Polygon:
		return "Polygon"
	elif vlayer.geometryType() == QGis.Line:
		return "LineString"
	elif vlayer.geometryType() == QGis.Point:
		return "Point"
	else:
		return False

# Compute area and perimeter of input polygon geometry
def getAreaAndPerimeter( geom ):
	measure = QgsDistanceArea()
	area = measure.measure( geom )			
	perim = measurePerimeter( geom, measure )
	return ( area, perim )

# Compute perimeter of input polygon geometry
def measurePerimeter( geom ):
	measure = QgsDistanceArea()
	value = 0.00
	polygon = geom.asPolygon()
	for line in polygon:
		value += measure.measureLine( line )
	return value

# Generate list of QgsPoints from input geometry ( can be point, line, or polygon )
def extractPoints( geom ):
	multi_geom = QgsGeometry()
	temp_geom = []
	if geom.type() == 0: # it's a point
		if geom.isMultipart():
			temp_geom = geom.asMultiPoint()
		else:
			temp_geom.append(geom.asPoint())
	if geom.type() == 1: # it's a line
		if geom.isMultipart():
			multi_geom = geom.asMultiPolyline() #multi_geog is a multiline
			for i in multi_geom: #i is a line
				temp_geom.extend( i )
		else:
			temp_geom = geom.asPolyline()
	elif geom.type() == 2: # it's a polygon
		if geom.isMultipart():
			multi_geom = geom.asMultiPolygon() #multi_geom is a multipolygon
			for i in multi_geom: #i is a polygon
				for j in i: #j is a line
					temp_geom.extend( j )
		else:
			multi_geom = geom.asPolygon() #multi_geom is a polygon
			for i in multi_geom: #i is a line
				temp_geom.extend( i )
	return temp_geom

# Check if two input field maps are unique, and resolve name issues if they aren't
def testForUniqueness( fieldList1, fieldList2 ):
	changed = True
	while changed:
		changed = False
		for i in fieldList1:
			for j in fieldList2:
				if j.name() == i.name():
					j = createUniqueFieldName( j )
					changed = True
	return fieldList2

# Create a unique field name based on input field name
def createUniqueFieldName( field ):
	check = field.name().right( 2 )
	if check.startsWith("_"):
		( val, test ) = check.right( 1 ).toInt()
		if test:
			if val < 2:
				val = 2
			else:
				val = val + 1
			field.setName( field.name().left( len( field.name() )-1 ) + unicode( val ) )
		else:
			field.setName( field.name() + "_2" )
	else:
		field.setName( field.name() + "_2" )
	return field

# Return list of names of all layers in QgsMapLayerRegistry
def getLayerNames( vTypes ):
	layermap = QgsMapLayerRegistry.instance().mapLayers()
	layerlist = []
	if vTypes == "all":
		for name, layer in layermap.iteritems():
			layerlist.append( unicode( layer.name() ) )
	else:
		for name, layer in layermap.iteritems():
			if layer.type() == QgsMapLayer.VectorLayer:
				if layer.geometryType() in vTypes:
					layerlist.append( unicode( layer.name() ) )
	return layerlist

# Return list of names of all fields from input QgsVectorLayer
def getFieldNames( vlayer ):
	fieldmap = getFieldList( vlayer )
	fieldlist = []
	for name, field in fieldmap.iteritems():
		if not field.name() in fieldlist:
			fieldlist.append( unicode( field.name() ) )
	return fieldlist

# Return QgsVectorLayer from a layer name ( as string )
def getVectorLayerByName( myName ):
	layermap = QgsMapLayerRegistry.instance().mapLayers()
	for name, layer in layermap.iteritems():
		if layer.type() == QgsMapLayer.VectorLayer and layer.name() == myName:
			if layer.isValid():
				return layer
			else:
				return None
				
# Return QgsMapLayer from a layer name ( as string )
def getMapLayerByName( myName ):
	layermap = QgsMapLayerRegistry.instance().mapLayers()
	for name, layer in layermap.iteritems():
		if layer.name() == myName:
			if layer.isValid():
				return layer
			else:
				return None

# Return the field list of a vector layer
def getFieldList( vlayer ):
	vprovider = vlayer.dataProvider()
	feat = QgsFeature()
	allAttrs = vprovider.attributeIndexes()
	vprovider.select( allAttrs )
	myFields = vprovider.fields()
	return myFields             

# Convinience function to create a spatial index for input QgsVectorDataProvider
def createIndex( provider ):
	feat = QgsFeature()
	index = QgsSpatialIndex()
	provider.rewind()
	while provider.nextFeature( feat ):
		index.insertFeature( feat )
	return index

# Convinience function to add a vector layer to canvas based on input shapefile path ( as string )
def addShapeToCanvas( shapeFilePath ):
	shapeFilePathList = shapeFilePath.split( "/" )
	layerName = QString( shapeFilePathList[len(shapeFilePathList)-1] )
	if layerName.endsWith( ".shp" ):
		layerName = unicode( layerName ).rstrip( ".shp" )
	vlayer_new = QgsVectorLayer( shapeFilePath, layerName, "ogr" )

	if vlayer_new.isValid():
		QgsMapLayerRegistry.instance().addMapLayer(vlayer_new)
		return True
	else:   
		return False

# Return all unique values in field based on field index
def getUniqueValues( provider, index ):
	allAttrs = provider.attributeIndexes()    
	provider.select( allAttrs )
	f = QgsFeature()
	values = []
	check = []
	while provider.nextFeature( f ):
		if not f.attributeMap()[ index ].toString() in check:
			values.append( f.attributeMap()[ index ] )
			check.append( f.attributeMap()[ index ].toString() )
	return values

# Generate a save file dialog with a dropdown box for choosing encoding style
def saveDialog( parent ):
	settings = QSettings()
	dirName = settings.value( "/UI/lastShapefileDir" ).toString()
	filtering = QString( "Shapefiles (*.shp)" )
	encode = settings.value( "/UI/encoding" ).toString()
	fileDialog = QgsEncodingFileDialog( parent, "Save output shapefile", dirName, filtering, encode )
	fileDialog.setDefaultSuffix( QString( "shp" ) )
	fileDialog.setFileMode( QFileDialog.AnyFile )
	fileDialog.setAcceptMode( QFileDialog.AcceptSave )
	fileDialog.setConfirmOverwrite( True )
	if not fileDialog.exec_() == QDialog.Accepted:
			return None, None
	files = fileDialog.selectedFiles()
	settings.setValue("/UI/lastShapefileDir", QVariant( QFileInfo( unicode( files.first() ) ).absolutePath() ) )
	return ( unicode( files.first() ), unicode( fileDialog.encoding() ) )