From my perspective the best approach for
floating adjustments would be the method used in PaintShop Pro. Here are two images of the PSP gamma corrector:
1. PSP adjustment dialog without thumbnails (30k):
http://www.jfcinc.net/Interfaces/XNView/pspfloat.jpg
Notice the ability to either lock the image to the adjustment, or just "apply" whenever. Also notice the ability to name, save, and recall adjustments.
2. PSP adjustment dialog with thumbnails (49k):
http://www.jfcinc.net/Interfaces/XNView/psppreview1.jpg
Here I have shown the thumbnail view. Notice that the dialog is now resizeable. Resize the dialog and the thumbnails also resize. You can even maximize the dialog. Notice the zoom in and out buttons. Also, see that little "4-arrows" button below/between the thumbnails? That's the image overview/navigator. See the next image:
3. PSP adjustment dialog with thumbs and navigator (51k):
http://www.jfcinc.net/Interfaces/XNView/psppreview2.jpg
Of course, you can always drag the thumbnail contents to reposition the image.
The flexibility shown here is insanely great and brings me back to PSP over and over again. The only things missing are the ability to specify the initial zoom (always 100% in PSP 9) and show only the adjusted thumb a la Corel PhotoPaint (whose adjustment thumbs are NOT adjustable in size).
This approach to the adjustment dialog is
de rigeur in my opinion. Any other design for a
floating adjustment dialog with thumbs (but see below) is substandard and lacking.
Another approach:
PhotoFilter allows adjustment directly from the toolbar. This is what I really want to see in XNView, though
in addition to the dialog,
not instead of! For most purposes, this the most efficient way for me to tweak an image.
4. PhotoFilter Toolbar (12k):
http://www.jfcinc.net/Interfaces/XNView ... ttools.jpg
Finally, I also really like Raw Shooter's approach:
5. Raw Shooter Essentials (40k):
http://www.jfcinc.net/Interfaces/XNView/rs1.jpg
Adjustment controls live in the sidebar and affect the image directly as in PhotoFiltre (and many other apps), that is: no adjustment dialog with thumbs. What is cool about Raw Shooter are those tabs (numbered 1,2, etc) at the top of the image. They store different sets of adjustments (even between sessions!!!!) that have already been applied to the image. I can adjust, save the adjustment to a tab, then make another adjustment, save it also to a tab, then switch back and forth between tabs to compare. Adjustments rendered to the actual file are delayed until you decide (even if it is next week or after a reboot), so everything is undoable.
I realize Raw Shooter is a RAW utility and adjustments to RAW files follow different paradigms from jpgs, tiffs, etc. Nevertheless...
Some combination of ALL of the above approaches in XNView would be absolutely the cat's meow.