If I open an image in the fullscreen viewer, press 1/2 for rotating, it can not be saved since rotating seems not to be an actual "change". That's a little bit irritating since I often want to correct the rotation of incoming images.
You can use File > Save As to save a new copy from the viewer, choosing to overwrite the original file if you wish.
However, you're better off using either the lister's Tools > Convert Images menu (or similar commands) or the Metadata panel to rotate images, since they will rotate things losslessly if possible. (The former will try to do lossless JPEG rotation. The latter will update the rotation field in the EXIF tags, although not all software respects it.)
OTOH, the viewer always saves and re-compresses a new version of the bitmap it is currently showing, which can result in a loss of quality with JPG images.
I think I will go with a dedicated hotkey that can be used in the fullscreen viewer to rotate the image in place.
Image ROTATE=90 REPLACE HERE
Image ROTATE=-90 REPLACE HERE
You can set up hotkeys for those commands in the lister, but they won't work in the fullscreen viewer.
The fullscreen viewer does not currently support user-defined hotkeys (except system-wide hotkeys, which would not make sense for this).
Hmm ok, that makes it difficult to get an easy (one keypress) solution. Wouldn't it be feasible to let 1/2 based rotating feature flagging the image as saveable? Then I can press 1/2 and CTRL-S and everything is fine!
Just a note of a small inconsistency: If I change an image in-place by using a hotkey (e.g. "Image ROTATE=90 REPLACE HERE") the selection/focus is lost. After the operation is completed (subsecond) everything is updated but the file selection is lost. Is this as expected?
Yes, if you have Preferences / File Operations / Options / Deselect files used in functions turned on, and have not added @nodeselect to the command, then it would be a bug if it didn't deselect the file.
Ok, I checked that and it seems to be a bug (DOpus 10.5.2.0) since the given option is turned off. I also noticed that the (docked) viewer pane isn't updated on selecting the rotated image again. I have to manually select an other file and then come back to the rotated image to update the viewer pane.
Ah, it may be because the old file is deleted and replaced by a new one. Might be something we can improve in the future.
Shameless hijack of thread to advocate the goodness of getting Viewer-contextual hotkey control, codes for currently viewed image (unless normal {f} codes will operate on the currently viewed image vs files selected in the lister), customization of the context menu, and some more control over mouse behavior (dbl-click, contrl keys on clicks, etc).