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

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

"""
***************************************************************************
    Grid.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__ = '$Format:%H$'

import math

from PyQt4.QtCore import QVariant
from qgis.core import QgsRectangle, QgsCoordinateReferenceSystem, QGis, QgsField, QgsFeature, QgsGeometry, QgsPoint
from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
from processing.core.parameters import ParameterExtent
from processing.core.parameters import ParameterNumber
from processing.core.parameters import ParameterSelection
from processing.core.parameters import ParameterCrs
from processing.core.outputs import OutputVector


class Grid(GeoAlgorithm):
    TYPE = 'TYPE'
    EXTENT = 'EXTENT'
    HSPACING = 'HSPACING'
    VSPACING = 'VSPACING'
    CRS = 'CRS'
    OUTPUT = 'OUTPUT'

    def defineCharacteristics(self):
        self.name, self.i18n_name = self.trAlgorithm('Create grid')
        self.group, self.i18n_group = self.trAlgorithm('Vector creation tools')

        self.types = [self.tr('Rectangle (line)'),
                      self.tr('Rectangle (polygon)'),
                      self.tr('Diamond (polygon)'),
                      self.tr('Hexagon (polygon)')]

        self.addParameter(ParameterSelection(self.TYPE,
                                             self.tr('Grid type'), self.types))
        self.addParameter(ParameterExtent(self.EXTENT,
                                          self.tr('Grid extent')))
        self.addParameter(ParameterNumber(self.HSPACING,
                                          self.tr('Horizontal spacing'), default=10.0))
        self.addParameter(ParameterNumber(self.VSPACING,
                                          self.tr('Vertical spacing'), default=10.0))
        self.addParameter(ParameterCrs(self.CRS, 'Grid CRS'))

        self.addOutput(OutputVector(self.OUTPUT, self.tr('Grid')))

    def processAlgorithm(self, progress):
        idx = self.getParameterValue(self.TYPE)
        extent = self.getParameterValue(self.EXTENT).split(',')
        hSpacing = self.getParameterValue(self.HSPACING)
        vSpacing = self.getParameterValue(self.VSPACING)
        crs = QgsCoordinateReferenceSystem(self.getParameterValue(self.CRS))

        bbox = QgsRectangle(float(extent[0]), float(extent[2]),
                            float(extent[1]), float(extent[3]))

        width = bbox.width()
        height = bbox.height()
        centerX = bbox.center().x()
        centerY = bbox.center().y()
        #~ originX = centerX - width / 2.0
        #~ originY = centerY - height / 2.0
        originX = bbox.xMinimum()
        originY = bbox.yMaximum()

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

        if width < hSpacing:
            raise GeoAlgorithmExecutionException(
                self.tr('Horizontal spacing is too small for the covered area'))

        if height < vSpacing:
            raise GeoAlgorithmExecutionException(
                self.tr('Vertical spacing is too small for the covered area'))

        #if self.types[idx].find(self.tr('polygon')) >= 0:
        if idx != 0:
            geometryType = QGis.WKBPolygon
        else:
            geometryType = QGis.WKBLineString

        fields = [QgsField('left', QVariant.Double, '', 24, 16),
                  QgsField('top', QVariant.Double, '', 24, 16),
                  QgsField('right', QVariant.Double, '', 24, 16),
                  QgsField('bottom', QVariant.Double, '', 24, 16)
                  ]

        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(fields,
                                                                     geometryType, crs)

        if idx == 0:
            self._rectangleGridLine(
                writer, width, height, originX, originY, hSpacing, vSpacing)
        elif idx == 1:
            self._rectangleGridPoly(
                writer, width, height, originX, originY, hSpacing, vSpacing)
        elif idx == 2:
            self._diamondGrid(
                writer, width, height, originX, originY, hSpacing, vSpacing)
        elif idx == 3:
            self._hexagonGrid(
                writer, width, height, originX, originY, hSpacing, vSpacing)

        del writer

    def _rectangleGridLine(self, writer, width, height, originX, originY,
                           hSpacing, vSpacing):
        ft = QgsFeature()

        columns = int(math.ceil(float(width) / hSpacing))
        rows = int(math.ceil(float(height) / vSpacing))

        # Longitude lines
        for col in xrange(0, columns + 1):
            polyline = []
            x = originX + (col * hSpacing)
            for row in xrange(0, rows + 1):
                y = originY - (row * vSpacing)
                polyline.append(QgsPoint(x, y))

            ft.setGeometry(QgsGeometry.fromPolyline(polyline))
            ft.setAttributes([x, originY, x, originY + (rows * vSpacing)])
            writer.addFeature(ft)

        # Latitude lines
        for row in xrange(0, rows + 1):
            polyline = []
            y = originY - (row * vSpacing)
            for col in xrange(0, columns + 1):
                x = originX + (col * hSpacing)
                polyline.append(QgsPoint(x, y))

            ft.setGeometry(QgsGeometry.fromPolyline(polyline))
            ft.setAttributes([originX, y, originX + (col * hSpacing), y])
            writer.addFeature(ft)

    def _rectangleGridPoly(self, writer, width, height, originX, originY,
                           hSpacing, vSpacing):
        ft = QgsFeature()

        columns = int(math.ceil(float(width) / hSpacing))
        rows = int(math.ceil(float(height) / vSpacing))

        for col in xrange(0, columns):
            # (column + 1) and (row + 1) calculation is used to maintain
            # topology between adjacent shapes and avoid overlaps/holes
            # due to rounding errors
            x1 = originX + (col * hSpacing)
            x2 = originX + ((col + 1) * hSpacing)
            for row in xrange(0, rows):
                y1 = originY - (row * vSpacing)
                y2 = originY - ((row + 1) * vSpacing)

                polyline = []
                polyline.append(QgsPoint(x1, y1))
                polyline.append(QgsPoint(x2, y1))
                polyline.append(QgsPoint(x2, y2))
                polyline.append(QgsPoint(x1, y2))
                polyline.append(QgsPoint(x1, y1))

                ft.setGeometry(QgsGeometry.fromPolygon([polyline]))
                ft.setAttributes([x1, y1, x2, y2])
                writer.addFeature(ft)

    def _diamondGrid(self, writer, width, height, originX, originY,
                     hSpacing, vSpacing):
        ft = QgsFeature()

        halfHSpacing = hSpacing / 2
        halfVSpacing = vSpacing / 2

        columns = int(math.ceil(float(width) / halfHSpacing))
        rows = int(math.ceil(float(height) / vSpacing))

        for col in xrange(0, columns):
            x1 = originX + ((col + 0) * halfHSpacing)
            x2 = originX + ((col + 1) * halfHSpacing)
            x3 = originX + ((col + 2) * halfHSpacing)

            for row in xrange(0, rows):
                if (col % 2) == 0:
                    y1 = originY - (((row * 2) + 0) * halfVSpacing)
                    y2 = originY - (((row * 2) + 1) * halfVSpacing)
                    y3 = originY - (((row * 2) + 2) * halfVSpacing)
                else:
                    y1 = originY - (((row * 2) + 1) * halfVSpacing)
                    y2 = originY - (((row * 2) + 2) * halfVSpacing)
                    y3 = originY - (((row * 2) + 3) * halfVSpacing)

                polyline = []
                polyline.append(QgsPoint(x1, y2))
                polyline.append(QgsPoint(x2, y1))
                polyline.append(QgsPoint(x3, y2))
                polyline.append(QgsPoint(x2, y3))
                polyline.append(QgsPoint(x1, y2))

                ft.setGeometry(QgsGeometry.fromPolygon([polyline]))
                ft.setAttributes([x1, y1, x3, y3])
                writer.addFeature(ft)

    def _hexagonGrid(self, writer, width, height, originX, originY,
                     hSpacing, vSpacing):
        ft = QgsFeature()

        # To preserve symmetry, hspacing is fixed relative to vspacing
        xVertexLo = 0.288675134594813 * vSpacing
        xVertexHi = 0.577350269189626 * vSpacing
        hSpacing = xVertexLo + xVertexHi

        halfVSpacing = vSpacing / 2

        columns = int(math.ceil(float(width) / hSpacing))
        rows = int(math.ceil(float(height) / vSpacing))

        for col in xrange(0, columns):
            # (column + 1) and (row + 1) calculation is used to maintain
            # topology between adjacent shapes and avoid overlaps/holes
            # due to rounding errors
            x1 = originX + (col * hSpacing)         # far left
            x2 = x1 + (xVertexHi - xVertexLo)       # left
            x3 = originX + ((col + 1) * hSpacing)   # right
            x4 = x3 + (xVertexHi - xVertexLo)       # far right

            for row in xrange(0, rows):
                if (col % 2) == 0:
                    y1 = originY - (((row * 2) + 0) * halfVSpacing) # hi
                    y2 = originY - (((row * 2) + 1) * halfVSpacing) # mid
                    y3 = originY - (((row * 2) + 2) * halfVSpacing) # lo
                else:
                    y1 = originY - (((row * 2) + 1) * halfVSpacing) # hi
                    y2 = originY - (((row * 2) + 2) * halfVSpacing) # mid
                    y3 = originY - (((row * 2) + 3) * halfVSpacing) # lo

                polyline = []
                polyline.append(QgsPoint(x1, y2))
                polyline.append(QgsPoint(x2, y1))
                polyline.append(QgsPoint(x3, y1))
                polyline.append(QgsPoint(x4, y2))
                polyline.append(QgsPoint(x3, y3))
                polyline.append(QgsPoint(x2, y3))
                polyline.append(QgsPoint(x1, y2))

                ft.setGeometry(QgsGeometry.fromPolygon([polyline]))
                ft.setAttributes([x1, y1, x4, y3])
                writer.addFeature(ft)