For the toolbar icons there is the choice for small or large icons.
Small uses 16x16, large 32x32, which I find either a bit too small or too large.
Is there a way to use 24x24 icons there? (without changing Windows settings that may affect things elsewhere)
I read somewhere that Directory Opus' own icons are designed at 22x22?
If that is the case, could I create 22x22 icons myself, and would they display pixel-perfect?
Toolbar icons can be any size you want. You can replace the internal icons. See the icons area here on the forum for examples.
I'm sorry, I can't seem to figure it out.
Most modern .ico's contain 16/24/32/48/256 image sizes already.
Isn't there a way to just tell Directory Opus to use the 24x24 image size for the toolbar?
I also experimented with icon files that contain only one image size.
One that is 22x22 and one that is 24x24.
But irrespectively if I choose small/large/default they turn out ugly in the toolbar:
What am I missing please?
Put prefered iconset on top of list in prefs.
Original default sizes were 22x22 and 32x32 pixel, but that is variable today.
Thanks for the fast response.
I have no idea how to do what you suggest.
To be clear, I am talking about icons for e.g. applications that can be triggered using the toolbar.
I am not talking about icon sets that replace all default DO icons.
(is that perhaps what you are talking about?)
P.S.
It looks like I mistyped 'Toolbar' in the title.
For the sake of others doing forum searches on the same matter, perhaps a mod could correct it?
If you don't want to replace/resize* the internal icon set, turn off Preferences / Toolbars / Appearance / Scale Toolbar button images when larger than standard size so your other icons don't get resized to the standard size when larger.
I would also recommend using PNG icons instead of .ico files, so you have full control over which size is selected. ICO files are subject to system-wide Windows rules for large/small size selection.
(*The internal set has various sizes for different DPIs and can also be made to scale those images to arbitrary sizes beyond that. An XML file can change which size is used for which DPI.)
You should be able to correct it yourself, but I'll do it.
Yes, then I misunderstood.
That was 'off' already.
I'll do some testing using png's instead of ico's soon.
b.t.w., I hate to reference competitors when using another companies' fora, but until now I've been using TC, and there you can set specific icon sizes for the toolbar. Perhaps that's an idea/suggestion for DO?
But it's probably just me having a hard time learning new ways 
Using a png image instead of an icon file indeed seems to give good results.
Luckily I am able to extract such png's from existing icon files (from e.g. Excel, Photoshop etc.) but I am guessing that's not something the average user is willing or able to do.
Anyway, I now know how to circumvent this problem, so thanks again for the prompt replies and support. Pretty impressive.
It's easily done using various tools, but I'm also guessing the average user* is happy with the standard, system-wide "large" and "small" icon sizes for their DPI, which is what Opus will load for .ico files (what Windows will load, in fact; Opus just asks Windows when it comes to .ico files). Most .ico files lack the intermediate sizes as well.
(*The average user of the subset that wants to use additional toolbar icons. The real average user probably isn't changing these things at all.)
Considering your knowledge and experience I am sure what you are saying is valid.
Yet as a new user, I just find 'small' to small, and 'large' to large.
And the fact that the developers decided on 22x22 pixels for the default icons confirms my opinion on that.
Most of the applications I am using do provide either 24, 48, or 256 px. size icons, so it shouldn't be too hard for DO to use those to render them to something less ugly than it currently does, and at a desired size.
I'll manage by extracting images from the original icons, resizing them, and saving them to 24x24 png's, but it feels like a time consuming exercise that could be avoided if DO had some more advanced handling and settings for icons.
In first line DO is an advanced filemanager with lots of options and iconsize of course depends on which screensize and resolution you use.
I use 38'' with 3840x1600 @ 125 dpi with only 32x32 px, and icons are sharp and size ok. On 10'' with 2736x1824 @ 200 dpi with mixed 22/32 px, same. For me.
BTW just resizing icons will never lead into best results. Esp. default set has got different details/appearance between 22/32, as some details are not possible with 22 (and also 24) px.
True, that's why I was hoping that if an icon file contains a 24x24 image, you could set DO to use it.
It's easier (for me) to edit an icon file to make sure it includes a 24x24 image, than additionally creating 24x24 png files for DO only.
Anyway, it's probably me needing to adjust being used to TC, and using image files instead of icon files does work well.