Is there a way of scaling the wallpaper in KDE while maintaining the aspect ratio?

I want to display all of the image I have set to my wallpaper while maintaining its aspect ratio. The obvious way of doing this would be to scale the image as appropriate and then use a background colour for the rest of the screen. It feels like there should be a setting for this but I could not find it? Is there a way of doing this without resizing the image?