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1e13d733c2
initAlgorithm() method This allows 2 benefits: - algorithms can be subclassed and have subclasses add additional parameters/outputs to the algorithm. With the previous approach of declaring parameters/outputs in the constructor, it's not possible to call virtual methods to add additional parameters/ outputs (since you can't call virtual methods from a constructor). - initAlgorithm takes a variant map argument, allowing the algorithm to dynamically adjust its declared parameters and outputs according to this configuration map. This potentially allows model algorithms which can be configured to have variable numbers of parameters and outputs at run time. E.g. a "router" algorithm which directs features to one of any number of output sinks depending on some user configured criteria.
83 lines
2.8 KiB
Python
83 lines
2.8 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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RasterLayerHistogram.py
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---------------------
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Date : January 2013
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Copyright : (C) 2013 by Victor Olaya
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Email : volayaf at gmail dot com
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************
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"""
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__author__ = 'Victor Olaya'
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__date__ = 'January 2013'
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__copyright__ = '(C) 2013, Victor Olaya'
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# This will get replaced with a git SHA1 when you do a git archive
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__revision__ = '$Format:%H$'
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import plotly as plt
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import plotly.graph_objs as go
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from qgis.core import (QgsApplication,
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QgsProcessingUtils)
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from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
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from processing.core.parameters import ParameterNumber
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from processing.core.parameters import ParameterRaster
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from processing.core.outputs import OutputHTML
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from processing.tools import raster
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class RasterLayerHistogram(QgisAlgorithm):
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INPUT = 'INPUT'
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BINS = 'BINS'
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PLOT = 'PLOT'
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def group(self):
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return self.tr('Graphics')
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def __init__(self):
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super().__init__()
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def initAlgorithm(self, config=None):
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self.addParameter(ParameterRaster(self.INPUT,
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self.tr('Input layer')))
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self.addParameter(ParameterNumber(self.BINS,
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self.tr('Number of bins'), 2, None, 10))
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self.addOutput(OutputHTML(self.PLOT, self.tr('Histogram')))
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def name(self):
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return 'rasterlayerhistogram'
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def displayName(self):
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return self.tr('Raster layer histogram')
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def processAlgorithm(self, parameters, context, feedback):
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layer = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT), context)
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nbins = self.getParameterValue(self.BINS)
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output = self.getOutputValue(self.PLOT)
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# ALERT: this is potentially blocking if the layer is too big
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values = raster.scanraster(layer, feedback)
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valueslist = []
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for v in values:
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if v is not None:
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valueslist.append(v)
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data = [go.Histogram(x=valueslist,
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nbinsx=nbins)]
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plt.offline.plot(data, filename=output, auto_open=False)
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