Associate and Opening Images with Irfanview

Is there a way like in Power Desk to Open and Associate all images to open all the time with another program than the Directory Opus Viewer without telling to do it everytime ?
Thanks !
Bob Le Vent

Opus should use the same filetype associations as Explorer and the rest of the operating system, except that there's an option in Opus which overrides this for image files.

If you don't want to use the Opus viewer on double-click then change the setting of Preferences / Double-Click / Files: Use internal picture viewer for....

After doing that you just have to make sure that Irfanview is associated with the image filetypes you're interested in, as normal.

Thanks NUDEL it works perfectly !