QGIS/python/plugins/processing/algs/qgis/Gridify.py

# -*- coding: utf-8 -*-

"""
***************************************************************************
    Gridify.py
    ---------------------
    Date                 : May 2010
    Copyright            : (C) 2010 by Michael Minn
    Email                : pyqgis at michaelminn dot com
***************************************************************************
*                                                                         *
*   This program is free software; you can redistribute it and/or modify  *
*   it under the terms of the GNU General Public License as published by  *
*   the Free Software Foundation; either version 2 of the License, or     *
*   (at your option) any later version.                                   *
*                                                                         *
***************************************************************************
"""

__author__ = 'Michael Minn'
__date__ = 'May 2010'
__copyright__ = '(C) 2010, Michael Minn'

# This will get replaced with a git SHA1 when you do a git archive

__revision__ = '$Format:%H$'

from PyQt4.QtCore import *
from qgis.core import *
from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.core.GeoAlgorithmExecutionException import \
        GeoAlgorithmExecutionException
from processing.core.ProcessingLog import ProcessingLog
from processing.core.parameters import ParameterVector
from processing.core.parameters import ParameterNumber
from processing.core.outputs import OutputVector

from processing.tools import dataobjects, vector

class Gridify(GeoAlgorithm):
    INPUT = 'INPUT'
    HSPACING = 'HSPACING'
    VSPACING = 'VSPACING'
    OUTPUT = 'OUTPUT'

    def defineCharacteristics(self):
        self.name = 'Snap points to grid'
        self.group = 'Vector general tools'

        self.addParameter(ParameterVector(
            self.INPUT, 'Input Layer', [ParameterVector.VECTOR_TYPE_ANY]))
        self.addParameter(ParameterNumber(
            self.HSPACING, 'Horizontal spacing', default=0.1))
        self.addParameter(ParameterNumber(
            self.VSPACING, 'Vertical spacing', default=0.1))

        self.addOutput(OutputVector(self.OUTPUT, 'Output'))

    def processAlgorithm(self, progress):
        layer = dataobjects.getObjectFromUri(
                self.getParameterValue(self.INPUT))
        hSpacing = self.getParameterValue(self.HSPACING)
        vSpacing = self.getParameterValue(self.VSPACING)

        if hSpacing <= 0 or vSpacing <= 0:
            raise GeoAlgorithmExecutionException(
                'Invalid grid spacing: %s/%s' % (hSpacing, vSpacing))

        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(
            layer.pendingFields(), layer.wkbType(), layer.crs())

        features = vector.features(layer)

        count = len(features)
        total = 100.0 / float(count)

        for count, f in enumerate(features):
            geom = f.geometry()
            geomType = geom.wkbType()

            if geomType == QGis.WKBPoint:
                points = self._gridify([geom.asPoint()], hSpacing, vSpacing)
                newGeom = QgsGeometry.fromPoint(points[0])
            elif geomType == QGis.WKBMultiPoint:
                points = self._gridify(geom.aMultiPoint(), hSpacing, vSpacing)
                newGeom = QgsGeometry.fromMultiPoint(points)
            elif geomType == QGis.WKBLineString:
                points = self._gridify(geom.asPolyline(), hSpacing, vSpacing)
                if len(points) < 2:
                    ProcessingLog.addToLog(Processing.LOG_INFO,
                        'Failed to gridify feature with FID %s' % f.id())
                    newGeom = None
                else:
                    newGeom = QgsGeometry.fromPolyline(points)
            elif geomType == QGis.WKBMultiLineString:
                polyline = []
                for line in geom.asMultiPolyline():
                    points = self._gridify(line, hSpacing, vSpacing)
                    if len(points) > 1:
                        polyline.append(points)
                if len(polyline) <= 0:
                    ProcessingLog.addToLog(Processing.LOG_INFO,
                        'Failed to gridify feature with FID %s' % f.id())
                    newGeom = None
                else:
                    newGeom = QgsGeometry.fromMultiPolyline(polyline)

            elif geomType == QGis.WKBPolygon:
                polygon = []
                for line in geom.asPolygon():
                    points = self._gridify(line, hSpacing, vSpacing)
                    if len(points) > 1:
                        polygon.append(points)
                if len(polygon) <= 0:
                    ProcessingLog.addToLog(Processing.LOG_INFO,
                        'Failed to gridify feature with FID %s' % f.id())
                    newGeom = None
                else:
                    newGeom = QgsGeometry.fromPolygon(polygon)
            elif geomType == QGis.WKBMultiPolygon:
                multipolygon = []
                for polygon in geometry.asMultiPolygon():
                    newPolygon = []
                    for line in polygon:
                        points = self._gridify(line, hSpacing, vSpacing)
                        if len(points) > 2:
                            newPolygon.append(points)

                    if len(newPolygon) > 0:
                        multipolygon.append(newPolygon)

                if len(multipolygon) <= 0:
                    ProcessingLog.addToLog(Processing.LOG_INFO,
                        'Failed to gridify feature with FID %s' % f.id())
                    newGeom = None
                else:
                    newGeom = QgsGeometry.fromMultiPolygon(multipolygon)

            if newGeom is not None:
                feat = QgsFeature()
                feat.setGeometry(newGeom)
                feat.setAttributes(f.attributes())
                writer.addFeature(feat)

            progress.setPercentage(int(count * total))

        del writer

    def _gridify(self, points, hSpacing, vSpacing):
        nPoints = []
        for p in points:
            nPoints.append(QgsPoint(round(p.x() / hSpacing, 0) * hSpacing,
                                    round(p.y() / vSpacing, 0) * vSpacing))

        i = 0
        # Delete overlapping points
        while i < len(nPoints) - 2:
            if nPoints[i] == nPoints[i + 1]:
                nPoints.pop(i + 1)
            else:
                i += 1

        i = 0
        # Delete line points that go out and return to the same place
        while i < len(nPoints) - 3:
            if nPoints[i] == nPoints[i + 2]:
                nPoints.pop(i + 1)
                nPoints.pop(i + 1)

                # Step back to catch arcs
                if i > 0:
                    i -= 1
            else:
                i += 1

        i = 0
        # Delete overlapping start/end points
        while len(nPoints) > 1 and nPoints[0] == nPoints[len(nPoints) - 1]:
            nPoints.pop(len(nPoints) - 1)

        return nPoints