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

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

"""
***************************************************************************
    RasterLayerHistogram.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 plotly as plt
import plotly.graph_objs as go

from qgis.core import (QgsApplication,
                       QgsProcessingUtils)
from processing.algs.qgis import QgisAlgorithm
from processing.core.parameters import ParameterNumber
from processing.core.parameters import ParameterRaster
from processing.core.outputs import OutputHTML
from processing.tools import raster


class RasterLayerHistogram(QgisAlgorithm):

    INPUT = 'INPUT'
    BINS = 'BINS'
    PLOT = 'PLOT'

    def icon(self):
        return QgsApplication.getThemeIcon("/providerQgis.svg")

    def svgIconPath(self):
        return QgsApplication.iconPath("providerQgis.svg")

    def group(self):
        return self.tr('Graphics')

    def __init__(self):
        super().__init__()
        self.addParameter(ParameterRaster(self.INPUT,
                                          self.tr('Input layer')))
        self.addParameter(ParameterNumber(self.BINS,
                                          self.tr('Number of bins'), 2, None, 10))

        self.addOutput(OutputHTML(self.PLOT, self.tr('Histogram')))

    def name(self):
        return 'rasterlayerhistogram'

    def displayName(self):
        return self.tr('Raster layer histogram')

    def processAlgorithm(self, parameters, context, feedback):
        layer = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT), context)
        nbins = self.getParameterValue(self.BINS)

        output = self.getOutputValue(self.PLOT)

        # ALERT: this is potentially blocking if the layer is too big
        values = raster.scanraster(layer, feedback)

        valueslist = []
        for v in values:
            if v is not None:
                valueslist.append(v)

        data = [go.Histogram(x=valueslist,
                             nbinsx=nbins)]
        plt.offline.plot(data, filename=output, auto_open=False)