FWIW, I've found that the "set as desktop wallpaper" command will place a "DOpus_Wallpaper.bmp" file in the My Documents folder. But when I hide it (because I like to keep the My Documents folder pretty clean), the command will no longer work. I either have to unhide it or delete the file. Is there a way around this?
What a strange bug, but I can confirm it. Not sure of a good workaround. You could make a button or hotkey which un-hides the file, then another button which hides it again, I guess:
<?xml version="1.0"?>
<button display="both" effect="gray">
<guid>{9B1D444F-9DA6-4A6B-9216-EF74C4105B0C}</guid>
<label>Unhide DOpus_Wallpaper.bmp</label>
<icon1>84</icon1>
<function type="batch">
<instruction>runmode hide</instruction>
<instruction>attrib -H "%HOMEPATH%\My Documents\DOpus_Wallpaper.bmp"</instruction>
</function>
</button>
That will unhide it. Copy the button and change the -H to a +H to hide it.
I have a similar command to hide/display my hidden files (I hide a lot of the OS files that aren't really informative). But it drove me nuts for quite awhile until I figured out why the "set as" command wasn't working.
Is there a way to change where this file is placed? For instance, if I could send it to [c:\Windows], I wouldn't really care if it's visible since that's such a dumping ground for various OS files.
I tried moving it to another directory, but the next time I place an image as the desktop wallpaper, a new file is created in MyDocs.
Naturally 
. This is where Dopus likes to copy the file used as the wallpaper. By doing it this way, if you moved, renamed, or deleted the original image file - you'd still have your wallpaper. Nudel filed a bug report for the impact 'hiding' the file has... we can submit a feature request as well to maybe be able to configure where the file gets stored (i.e. someplace other than my docs).
I have been waiting for a fix on this for a while. But, has the ability to change the location of the wallpaper file (DOpus_Wallpaper.bmp) to someplace other than My Documents ever made it into a feature request? Here is why I'd like to see it moved:
I always use Dopus viewer for viewing images. And I love the fact that I can simply right click and set as wallpaper. But since I have a laptop, a desktop and several VMs, and I keep the "my documents" folder synced between all them (this does not seem like an uncommon practice does it?), I find it very irritating that since the DOpus_Wallpaper.bmp gets synced, when I reboot my laptop my desktops wallpaper appears there and vice versa. Especially since my desktop is a 3 monitor setup and I use wallpaper to fit those monitors, where my laptop is only 1280x800. And worse yet, I set my laptop wallpaper back to a 1280x800 image, and then later reboot or logout/back in to my desktop system, and there is my small laptop image centered on each monitor. I end up in a vicious circle, Ugh...
To me it does not seem like the "My Documents" folder is a best practice location for this file, since it is not really file that would ever need to be user accessible. It seems like it would belong in AppData or something...
That's because Windows itself syncs the background image setting in your roaming profile.
If Opus didn't copy the file to somewhere which was synced as part of the profile then you'd end up with no backdrop at all when the profile was synced to another machine. Windows will always sync the setting saying "Use as the backdrop" and if doesn't exist on a particular machine then you get no image there.
I don't know if there's a way to make machine-specific backdrops instead of user-specific (i.e. profile-specific) ones, except by purposefully setting a local file to be the backdrop so that points to a different image -- which isn't in a synced folder -- on each machine.
Also, the bug this thread is about is fixed as far as I can tell. If the image is set as hidden Opus still changes it fine on my machine.
Yeah, it's not a bug anymore... but I think your request is logical even from my simple 1 resolution, 1 screen point of view.