Preview app resize photo not working following Big Sur install

Bailier -

I open a jpg in Preview or I open Preview and select a photo. The photo I choose or the directory location (local or network mount) makes no difference. In Preview I choose Tools > Adjust Size and then either Custom or I choose a preset like 1024 X 1024 (anything smaller than the original photo, other smaller options don't work either). I typically use Resolution of 72 with Scale Proportionally and Resample Image selected but other options for these don't seem to matter. The Resulting Size box in the menu indicates correctly that a resize will happen, for example "565 KB (was 1.3 MB)." When I select OK the photo indicates under the file name in Preview "Edited." File size in Finder does not change. When I select Save in Preview File size in Finder does not change. When I close the file in Preview the file size in Finder does not change. If I close Finder and reopen it the file size does not change. If I reboot the Mac and reopen Finder the file size does not change. If I attach the file to an email or to a text (using Messages for Web) and send the file the size is the original size (1.3MB for this example).

As you requested, I did reboot in Safe Mode and tried to resize a file using Preview. Same result, no resize.

I did find a way using Photos to resize but it is not something I would want to use all the time. You have to Import the photo to Photos and then Export the photo. During the export process there is some resize functionality. Would rather see Preview get fixed.

Thanks for looking at this for me. Appears I am not the only one with this problem but it looks like most have moved to third party apps and abandoned Preview.

I stumbled on the resolution. If you are using an iphone ios11 or newer to take photos and the iphone is using the default configuration then the photo file format might be the Apple proprietary HEIC format. That is what was happening to me. When I moved (AirDrop or cloud synch) the photos to my MAC they were still HEIC format. The Preview resize function works fine with jpeg files. The resize function appears to work on the HEIC format but it doesn't, the file doesn't change size.

Workaround for Preview for me is to open the HEIC files in Preview and then select File > Export and on the export menu select jpeg 2000 as the file format. Then I can open the file again as a jpeg 2000 file and it will resize correctly. Also changed phone configuration.

Contacted Apple support. They are aware of the problem and are working on it.

Thanks, I will post an update if I get a resolution.