PNG with alpha transparency & Thumbnail border glitch

Bug with Thumbnail borders as set in Directory Opus Colors/Thumbnails/Borders
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here is a SS of some PNG thumbnails (ontop of a background image)
with the above settings off
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and here they are with above settings on
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Other images do show a border, so I suspect the thumbnail border settings are more realistically thumbnail backgrounds
But as they say border I will mark this as a bug that needs attention please.

Maybe have another setting for thumbnail background (with command/property) as it is useful sometimes, though not 'colour aware' where a white icon with transparancy will be invisible on a white background.

The setting is a border around images without opacity, and is also used as the background for images with opacity. It isn't a bug. There isn't room in the UI to spell it out in that much detail.