Label / Text - RichText styling / theming

In QML, when using Label.text (or Text.text), with textFormat set to Text.RichText, theming is applied to the html. Because of that, there seems to be some kind of overlay or alpha channel (my guess is theming).

Result (sizing difference is because of scaling & screenshot):

How to achieve this:
Create a new QML project and add this below the ‘Hello Sailors’-label:

Label {
           id: contentLabel

           scale: 1
           //color: "#FF000000"

           transformOrigin: Item.TopLeft

           wrapMode: Text.WrapAtWordBoundaryOrAnywhere
           textFormat: Text.RichText
           //smooth: true

           text: "<img src=\"\" />"