Re: [QGIS-Developer] Mesh Layers: Way to update/repaint the QgsMeshRendererScalarSettingsWidget after recreating color ramp

[Richard Duivenvoorde via QGIS-Developer]

On 11/29/22 17:25, Vincent Cloarec wrote:

Hi Richard,

Can you precise how do you set the color ramp to the mesh layer ? Maybe you set 
only classes (color/value) ?

Hi Vincent,

Thanks for looking in my mail. These are my first Mesh experiments (using 
pyqgis). So maybe I'm totally off.
So yes, I'm only setting classes... Hoping that with that I'd also set the 
Color Ramp?

Usecase is: some model creates nc files (with 100 datagroups), the plugin or 
script should select one group (the one showing) and then either create some 
color ramp on the fly (logarithmic).
OR select a ramp which is not in the dropdown, but in the plugin as a .txt file 
like the one below

Thanks for any hints.

Regards,

Richard Duivenvoorde


++++ Below some for me working Python code: ++++

l = iface.mapCanvas().currentLayer()
# rs = RenderSettings
rs = l.rendererSettings()
# going to change the rendering settings...
# srs = ScalarRenderingSettings
srs = rs.scalarSettings(rs.activeScalarDatasetGroup())

# Trying to set the dataResamplingMethod to None (instead of NeighbourAverage)
# dataResamplingMethod = 1
# QgsMeshRendererScalarSettings.None = 0
# QgsMeshRendererScalarSettings.NeighbourAverage = 1
print(f'dataResamplingMethod: {srs.dataResamplingMethod()}')
# TODO: QgsMeshRendererScalarSettings.NeighbourAverage.None not usable in 
python?? https://github.com/qgis/QGIS/issues/51033
srs.setDataResamplingMethod(1)  # 0 = None, 1 = NeighbourAverage

# INTERPOLATION:DISCRETE
# https://api.qgis.org/api/qgscolorrampshaderwidget_8cpp_source.html
parsing_ok, color_ramp_items, color_ramp_shader_type, errors = 
QgsRasterRendererUtils.parseColorMapFile('/home/richard/z/22/rivm/1128_netcdf_styling/rgb3class.txt')
if parsing_ok:
    print(f'{len(color_ramp_items)} colorRampItems')
    color_ramp_shader_types = {
        0: 'QgsColorRampShader.Interpolated',
        1: 'QgsColorRampShader.Discrete'
    }
    print(f'ColorRampShaderType: 
{color_ramp_shader_types[color_ramp_shader_type]}')

    for cr in color_ramp_items:
        print(f'{cr} -- value: {cr.value} color: {cr.color} label: {cr.label}')
    print(f'Parsing OK')

    shader = QgsColorRampShader(minimumValue=0, maximumValue=24, 
colorRamp=None, type=QgsColorRampShader.Discrete, 
classificationMode=QgsColorRampShader.EqualInterval)
    shader.setColorRampItemList(color_ramp_items)
    shader.createColorRamp()
    srs.setColorRampShader(shader)
    srs.setOpacity(0.77)  # some transparency
else:
    print(f'Failed parsing the file, errors: {errors}')

# UPDATE the rendererSettings
rs.setScalarSettings(rs.activeScalarDatasetGroup(), srs)
l.setRendererSettings(rs)

l.rendererChanged.emit()
l.styleChanged.emit()

#QgsProject.instance().addMapLayer(l)


++++ Some (not logarithmic) color file export ++++

# QGIS Generated Color Map Export File
INTERPOLATION:DISCRETE
2,255,0,0,255,<= 2.000000
4,0,255,0,255,2.000000 - 4.000000
6,0,0,255,255,4.000000 - 6.000000
10,100,100,100,255,6.000000 - 10.000000



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