Legend graphics¶

By default, QWC will obtain the legend graphics of a layer from QGIS Server.

Customizing the GetLegendGraphics request¶

You can customize the GetLegendGraphics request by specifying additional query parameters in via extraLegendParameters in the theme configuration block. The list of supported query parameters is documented in the QGIS Server documentation.

Providing custom legend images¶

You can provide custom legend images by enabling the qwc-legend-service.

Mount the legend folder into the qwc-legend-service container, i.e.:

  qwc-legend-service:
    image: sourcepole/qwc-feature-info-service:vYYYY.MM.DD
    volumes:
      ...
      - ./volumes/legends:/legends

Note: If mounting to another location than /legends, set the legend_images_path in the legend service configuration in tenantConfig.json:

{
  "name": "legend",
  "config": {
    "legend_images_path": "/<path>/"
  }
}

Then, legend images will be searched for in this order (the first one found is used):

• A filename matching <legend_images_path>/<service_name>/<layername>_<style>_<suffix>.png
• A filename matching <legend_images_path>/<service_name>/<layername>_<suffix>.png
• A filename matching <legend_images_path>/<service_name>/default_<suffix>.png
• A filename matching <legend_images_path>/<service_name>/<layername>_<style>.png
• A filename matching <legend_images_path>/<service_name>/<layername>.png
• A filename matching <legend_images_path>/<resource_entry[legend_image]>
• A filename matching <legend_images_path>/<service_name>/default.png
• As base64, as set in <resource_entry[legend_image_base64]>

Where

• service_name is the name of the WMS service
• layername is the WMS layer name
• suffix: empty, or one of _thumbnail, _tooltip. The suffix is passed by QWC to the legend service depending on the requested image type.
• resource_entry[legend_image] and resource_entry[legend_image_base64] are the legend_image resp. legend_image_base64 settings of a layer as configurd in the legend service resource configuration, for example:

{
  "name": "legend",
  "config": ...,
  "resources": {
    "wms_services": [
      {
        "name": "<service name>",
        "root_layer": {
          "name": "<root_layer_name>",
          "layers": [
            {
              "name": "<layer_name>",
              "legend_image": "edit_points.png",
              "legend_image_base64": "<base64_string>"
            }
          ]
        }
      }
    ]
  }
}