Use a prerendered image for the layer legend

[jtroberts]

Purpose

• Use a prerendered image for the layer legend

Proposed Changes

• Allow a URL to an image in the existing "Legend From URL" configuration field for all valid layer types
• Check if legend URL is a valid image
• Display the image from the legend URL as the layer's legend graphic

Issues

• [New Feature]: Use a prerendered image for the layer legend #658

Testing

• Tested with legend URL pointing to a static image file: https://gibs.earthdata.nasa.gov/legends/GEDI_MU_Color_Index_V.svg
• Tested with legend URL pointing to a GetLegendGraphic request: https://gibs.earthdata.nasa.gov/wms/epsg4326/best/?version=1.3.0&service=WMS&request=GetLegendGraphic&sld_version=1.1.0&layer=GRanD_Dams&format=image/png&STYLE=default
• Tested with existing CSV files
• Tested with using legend configuration custom entries

[tariqksoliman]

Nice! One issue I see, and I this may be because I don't have many long legend items, but the legends from images are too small:

Could you perhaps add another configuration option to say how wide the image section is, or perhaps take the image width from the image and force the img to be that width (up until some max-width)?

Thanks!

[jtroberts]

I went with the second option and adjusted the legend width to match the image width up to a max-width of 300px. This looks better to me.

Two vertical legends:

Bunch of legends:

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[tariqksoliman]

Perfect, thanks!