Thanks @frjo . Have just read through How to use Image Processing using a short code? - #16 by bwintx , and it seems there is no way to do any image processing if the images are in /static. That said , @bep is able to do it with a mount.
There is a comment at How to use Image Processing using a short code? - #9 by jmooring that this needs the extended version of Hugo. I’m not using the extended version and it seems the theme has no Hugo pipes support - Add support for Hugo pipe SCSS · Issue #480 · kakawait/hugo-tranquilpeak-theme · GitHub
I have tried many example templates and code, all to no avail. The latest round of errors are of the type
execute of template failed at <$img.Resize>: nil pointer evaluating resource.Resource.Resize
so obviously the image can’t be found. I have tried putting the image in an /assets/images path, and also in the same path as the content, as well as the /static path. The MD code has had the image filename specified with an extension and without an extension. Considering now the time this has consumed, I’ll simply reduce the image size manually.