def fix_style(layer: QgsRasterLayer) -> None:
''' Sets a sensible default style for loaded raster layers and fix up other issues.
By default QGIS uses MultiBandColor renderer if there are multiple bands.
(See https://github.com/qgis/QGIS/blob/final-3_0_1/src/core/raster/qgsrasterlayer.cpp#L729).
This function picks the right renderers, either a palette or gray-band renderer.
Also, fake categories/classes that exist due to GDAL limitations are removed.
Search for UNUSED_CATEGORY_LABEL to find details. '''
provider = layer.dataProvider() # type: QgsRasterDataProvider
color_interp = provider.colorInterpretation(1)
is_palette = color_interp == QgsRaster.PaletteIndex
# See the link below on how to create default-type renderers.
# https://github.com/qgis/QGIS/blob/final-3_0_1/src/core/raster/qgsrasterrendererregistry.cpp#L128-L137
renderer = layer.renderer() # type: QgsRasterRenderer
new_renderer = None
if is_palette:
# For paletted layers we always re-create the renderer even if it is already a
# paletted renderer. This is because we need to remove the UNUSED categories.
color_table = provider.colorTable(1)
classes = QgsPalettedRasterRenderer.colorTableToClassData(color_table)
if not any(c.label == gis4wrf.core.UNUSED_CATEGORY_LABEL for c in classes):
return
new_classes = filter(lambda c: c.label != gis4wrf.core.UNUSED_CATEGORY_LABEL, classes)
new_renderer = QgsPalettedRasterRenderer(renderer.input(), 1, new_classes)
layer.setRenderer(new_renderer)
else:
if not isinstance(renderer, QgsSingleBandGrayRenderer):
new_renderer = QgsSingleBandGrayRenderer(renderer.input(), 1)
layer.setRenderer(new_renderer)
layer.setDefaultContrastEnhancement() # must be *after* setting the renderer
