widgets.py

            r = QgsMultiBandColorRenderer(None,
                ui.sliderRed.value(), ui.sliderGreen.value(), ui.sliderBlue.value())

            i = self.ui.comboBoxContrastEnhancement.currentIndex()
            alg = self.ui.comboBoxContrastEnhancement.itemData(i)

            if alg == QgsContrastEnhancement.NoEnhancement:
                r.setRedContrastEnhancement(None)
                r.setGreenContrastEnhancement(None)
                r.setBlueContrastEnhancement(None)
            else:
                rgbEnhancements = []
                for i in range(3):
                    e = QgsContrastEnhancement(self.sensor.bandDataType)
                    minmax = [float(self.multiBandMinValues[i].text()), float(self.multiBandMaxValues[i].text())]
                    cmin = min(minmax)
                    cmax = max(minmax)
                    e.setMinimumValue(cmin)
                    e.setMaximumValue(cmax)
                    e.setContrastEnhancementAlgorithm(alg)
                    rgbEnhancements.append(e)
                r.setRedContrastEnhancement(rgbEnhancements[0])
                r.setGreenContrastEnhancement(rgbEnhancements[1])
                r.setBlueContrastEnhancement(rgbEnhancements[2])

        if ui.stackedWidget.currentWidget() == ui.pageSingleBand:
            r = QgsSingleBandPseudoColorRenderer(None, ui.sliderSingleBand.value(), None)
            minmax = [float(ui.tbSingleBandMin.text()), float(ui.tbSingleBandMax.text())]
            cmin = min(minmax)
            cmax = max(minmax)
            r.setClassificationMin(cmin)
            r.setClassificationMax(cmax)
            colorRamp = self.ui.cbSingleBandColorRamp.currentColorRamp()

            # fix: QGIS 3.0 constructor
            shaderFunc = QgsColorRampShader(cmin, cmax)
            shaderFunc.setColorRampType(self.currentComboBoxItem(ui.cbSingleBandColorRampType))
            shaderFunc.setClip(True)
            nSteps = 10
            colorRampItems = []
            diff = cmax - cmin
            for i in range(nSteps + 1):
                f = float(i) / nSteps
                color = colorRamp.color(f)
                value = cmin + diff * f
                colorRampItems.append(QgsColorRampShader.ColorRampItem(value, color))
            shaderFunc.setColorRampItemList(colorRampItems)
            shader = QgsRasterShader()
            shader.setMaximumValue(cmax)
            shader.setMinimumValue(cmin)
            shader.setRasterShaderFunction(shaderFunc)
            r.setShader(shader)

            s = ""
        return r



class PropertyDialogUI(QDialog, loadUIFormClass(PATH_SETTINGSDIALOG_UI)):

    def __init__(self, parent=None):
        super(PropertyDialogUI, self).__init__(parent)
        self.setupUi(self)



if __name__ == '__main__':
    import site, sys
    #add site-packages to sys.path as done by enmapboxplugin.py

    from timeseriesviewer import DIR_SITE_PACKAGES
    site.addsitedir(DIR_SITE_PACKAGES)

    #prepare QGIS environment
    if sys.platform == 'darwin':
        PATH_QGS = r'/Applications/QGIS.app/Contents/MacOS'
        os.environ['GDAL_DATA'] = r'/usr/local/Cellar/gdal/1.11.3_1/share'
    else:
        # assume OSGeo4W startup
        PATH_QGS = os.environ['QGIS_PREFIX_PATH']
    assert os.path.exists(PATH_QGS)

    qgsApp = QgsApplication([], True)
    QApplication.addLibraryPath(r'/Applications/QGIS.app/Contents/PlugIns')
    QApplication.addLibraryPath(r'/Applications/QGIS.app/Contents/PlugIns/qgis')
    qgsApp.setPrefixPath(PATH_QGS, True)
    qgsApp.initQgis()

    #run tests
    #d = AboutDialogUI()
    #d.show()

    d = PropertyDialogUI()
    d.exec_()
    #close QGIS
    qgsApp.exec_()
    qgsApp.exitQgis()