QGIS: How to invert the values in a layout legend?

Question

At 3.16.3 I have added this legend to a map layout. Notice how the lowest value is at the top, with values increasing towards the bottom:

I would like to instead have the lowest value at the bottom, with values increasing towards the top, maintaining their associated color patches (blue = lowest value, pink = highest value). I used MS Paint to flip the image above to show the desired effect (of course this flipping also flips the text so that it is unreadable):

The QGIS documentation does not discuss such re-ordering the legend.

Nor have I found the ability to re-order in the Layer Styling panel, where the lowest value always is placed at the top:

Note that I'm not talking about inverting the color ramp. Rather, I want to invert the value order.

Answer 1

you can edit it manually, uncheck "Auto update" and use the arrows to reorder the values...yes, not that comfortable, but even better then flipping with MS Paint.

Answer 2

I believe this was addressed in the 3.18 release of QGIS but I haven't tried it yet. Feature: Color ramp legend improvements

Edit I tried the new feature with a raster DEM and it works as described. One thing to note though is that the Autoupdate needs to be turned off and you have to double click the legend item to access the additional item settings.

Answer 3

For now, here is a workaround in the form of a Python script. It's quite easy to use. Just paste the script below into a new editor in the Python console, open a print layout, select a legend in the layout, select a layer in the main window Table of contents, then run the script.

def invertLegendNodeOrder():
    open_layouts = iface.openLayoutDesigners()
    if not open_layouts:
        iface.messageBar().pushMessage('You have no open layouts')
        return
        
    layout = open_layouts[0].layout()
    legend = [i for i in layout.selectedLayoutItems() if isinstance(i, QgsLayoutItemLegend)]
    if not legend:
        iface.messageBar().pushMessage('Please select a legend in an open layout')
        return
        
    legend = legend[0]
    model = legend.model()
    layer = iface.activeLayer()
    layer_node = model.rootGroup().findLayer(layer)
    if not layer_node:
        iface.messageBar().pushMessage('Selected layer not found in layout legend')
        return
        
    cat_count = model.legendRootRowCount(layer_node)
    if not layer or not cat_count:
        iface.messageBar().pushMessage('Please select a layer with legend nodes')
        return
        
    order_property = layer_node.customProperty('legend/node-order')
    if order_property is not None: # A custom node order property has already been set
        current_order = [int(i) for i in order_property.split(',')]
        new_order = [i for i in reversed(current_order)]
    else:
        current_order = [i for i in range(cat_count)]
        new_order = [i for i in reversed(current_order)]

    QgsMapLayerLegendUtils.setLegendNodeOrder(layer_node, new_order)
    model.refreshLayerLegend(layer_node)
    legend.refresh()
    
              
invertLegendNodeOrder()

See the gif below for a short demonstration.

As you can see it works with both vector and raster layers.

This answer is partly based on an answer to a question I asked a while ago here:

Answer 4

EDIT : QGIS 3.18 now can do it easily (see answer above)

An other solution from the layer style panel

You can export the color map to a file, reorder the lines with a text editor and import the file again.

Step

1. Export the color map to a file (1 in the picture)
2. Open the file, reorder the lines and save the file
3. Open the file again (2 in the picture)

Answer 5

In the main map window (ie not the layout) go to the symbology settings for the layer in question (dNBR in your case), and click in the 'Values' heading in the 'classes' section. That should allow you to order the entries ascending/descending as you wish, without changing the color ramp order. Then go back to the legend settings of the layout window and refresh the legend and it should reorder automatically.