content: # -*- coding: utf-8 -*-
  
  """
  ***************************************************************************
      EquivalentNumField.py
      ---------------------
      Date                 : January 2013
      Copyright            : (C) 2013 by Victor Olaya
      Email                : volayaf at gmail 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__ = 'Victor Olaya'
  __date__ = 'January 2013'
  __copyright__ = '(C) 2013, Victor Olaya'
  # This will get replaced with a git SHA1 when you do a git archive
  __revision__ = '$Format:%H$'
  
  import matplotlib.pyplot as plt
  import matplotlib.pylab as lab
  from PyQt4.QtCore import *
  from qgis.core import *
  from processing.parameters.ParameterVector import ParameterVector
  from processing.parameters.ParameterTableField import ParameterTableField
  from processing.core.GeoAlgorithm import GeoAlgorithm
  from processing.outputs.OutputHTML import OutputHTML
  from processing.tools import *
  from processing.tools import dataobjects
  from processing.parameters.ParameterNumber import ParameterNumber
  
  class VectorLayerHistogram(GeoAlgorithm):
  
      INPUT = "INPUT"
      OUTPUT = "OUTPUT"
      FIELD = "FIELD"
      BINS = "BINS"
  
  
      def processAlgorithm(self, progress):
          uri = self.getParameterValue(self.INPUT)
          layer = dataobjects.getObjectFromUri(uri)
          fieldname = self.getParameterValue(self.FIELD)
          output = self.getOutputValue(self.OUTPUT)
          values = vector.getAttributeValues(layer, fieldname)
          plt.close()
          bins = self.getParameterValue(self.BINS)
          plt.hist(values[fieldname], bins)
          plotFilename = output +".png"
          lab.savefig(plotFilename)
          f = open(output, "w")
          f.write("<img src=\"" + plotFilename + "\"/>")
          f.close()
  
      def defineCharacteristics(self):
          self.name = "Vector layer histogram"
          self.group = "Graphics"
          self.addParameter(ParameterVector(self.INPUT, "Input layer", [ParameterVector.VECTOR_TYPE_ANY]))
          self.addParameter(ParameterTableField(self.FIELD, "Attribute", self.INPUT,ParameterTableField.DATA_TYPE_NUMBER))
          self.addParameter(ParameterNumber(self.BINS, "number of bins", 2, None, 10))
          self.addOutput(OutputHTML(self.OUTPUT, "Output"))
  
  