If you prefer some utility with a GUI there is the BIMP plugin for Gimp. https://alessandrofrancesconi.it/projects/bimp/
There is a built in watermark function where you can add regular text with varing opacity or a Graphic watermark where you would need to make the graphic with the required opacity.
Example:
...but yes when it comes to speed and efficiency ImageMagick wins.
Ahh...you are using linux. Which distro?
This is the BIMP I use in (k)buntu good chance it works on your installation.
Unzip. Put the file bimp2 in ~/.config/GIMP/2.10/plug-ins Check that it is still executable
There is a built in watermark function where you can add regular text with varing opacity or a Graphic watermark where you would need to make the graphic with the required opacity.
Example:
...but yes when it comes to speed and efficiency ImageMagick wins.
Ahh...you are using linux. Which distro?
This is the BIMP I use in (k)buntu good chance it works on your installation.
Unzip. Put the file bimp2 in ~/.config/GIMP/2.10/plug-ins Check that it is still executable