I am able to scale the size of an image using the text editor in the Text Block addon. This applies to both svg and png.
However, using the Image addon would be the obvious way to scale and publish an image. When I use the Image addon, the width and the height definition works on the edit page, but is ignored on the published page. Is it a bug that the syntax for width don't contain px, em or %? (I see that other users have had the same problem.)