Cartogram.py

#-----------------------------------------------------------
# 
# Cartogram Creator
#
# A QGIS plugin for creating cartograms based on polygon
# shapefile. Uses algorithm proposed in:
#     Dougenik, J. A, N. R. Chrisman, and D. R. Niemeyer. 1985.
#     "An algorithm to construct continuous cartograms."
#     Professional Geographer 37:75-81
#
# This plugin uses python code adapted from Eric Wolfs pyCartogram.py
# See plugin about dialog for more information.
#
# EMAIL: carson.farmer (at) gmail.com
# WEB  : www.carsonfarmer.com
#
#-----------------------------------------------------------
# 
# licensed under the terms of GNU GPL 2
# 
# 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.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
# 
#---------------------------------------------------------------------

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

import doCartogram
import resources
import os

class CartogramPlugin:
  def __init__(self, iface):
    # Save a reference to the QGIS iface
    self.iface = iface

  def initGui(self):
    # Create projection action
    self.action = QAction(QIcon(":/cartogram.png"), "Cartogram Creator", self.iface.mainWindow())
    self.action.setWhatsThis("Tool for creating rubber-sheet cartogram")
    QObject.connect(self.action, SIGNAL("activated()"), self.run)
    # Create about button
    self.helpaction = QAction(QIcon(":/cartogramhelp.png"), "About", self.iface.mainWindow())
    self.helpaction.setWhatsThis("Help for Cartogram Creator")
    QObject.connect(self.helpaction, SIGNAL("activated()"), self.helprun)

    # Add to the main toolbar
    self.iface.addToolBarIcon(self.action)
    self.iface.addPluginToMenu("&Cartogram Creator", self.action)
    self.iface.addPluginToMenu("&Cartogram Creator", self.helpaction)

  def unload(self):
    # Remove the plugin
    self.iface.removePluginMenu("&Cartogram Creator", self.action)
    self.iface.removePluginMenu("&Cartogram Creator", self.helpaction)
    self.iface.removeToolBarIcon(self.action)

  def helprun(self):
    # print "Help pressed..."
    infoString = QString("Written by Carson Farmer\ncarson.farmer@gmail.com\n")
    infoString = infoString.append("www.geog.uvic.ca/spar/carson\n")
    infoString = infoString.append("Code adapted from Eric Wolfs pyCartogram.py\n\n"
                                   + "This tool creates a new shapefile based on "
                                   + "the input shapefile with each polygon vertex shifted. "
                                   + "Should be called iteratively to get the results desired.\n")
    infoString = infoString.append("Based on a translation of Andy Agenda's ESRI ArcScript"
                                   + "for contiguous cartograms:\nhttp://arcscripts.esri.com/details.asp?dbid=10509\n")
    infoString = infoString.append("He based the routine on Charles B. Jackel's script in:\n"
                                   +"'Using ArcView to Create Contiguous and Noncontiguous Area Cartograms,'"
                                   +"Cartography and Geographic Information Systems, vol. 24, no. 2, 1997, pp. 101-109\n")
    infoString = infoString.append("Charles B. Jackel based his script on the method proposed in:\n"
                                   + "Dougenik, J. A, N. R. Chrisman, and D. R. Niemeyer. 1985. 'An algorithm "
                                   + "to construct continuous cartograms.' Professional Geographer 37:75-81")
    QMessageBox.information(self.iface.mainWindow(),"About Cartogram Creator",infoString)

  def run(self):
    d = doCartogram.Dialog(self.iface)
    d.exec_()