Some photos are sharp on the phone but low-res on icloud.com/photos My wife has an iPhone7 with &quot;Optimize iPhone Storage&quot; enabled, and an iCloud account with more than enough storage -- 77GByte of photos and 200GByte storage on iCloud.
She's gotten to be well aware of the implications of the storage optimization and the need to sometimes tap or pinch images on the phone to re-download a full-resolution image from iCloud to the phone, when it's needed.
However we seem to have the odd situation that, for a handful of images taken on the phone at various different times earlier in the year, when viewed in a web browser on a desktop PC at www.icloud.com/photos , those photos are fuzzy.  They're definitely still stored at full resolution on the phone, because she can email them from the phone and they're the expected size (4032x3024) and sharpness.  And the vast majority of images do seem to be full resolution in iCloud (accessed via www.icloud.com/photos ) , as expected.  No amount of adding the offending images to new albums, or duplicating those images and adding the duplicates, seems to help.
Downloading the image (using the download icon) from www.icloud.com/photos just retrieves a fuzzy version.
She does quite often use www.icloud.com/photos when working on a desktop PC to retrieve her images there, so it'd be nice to have access to all of them there at full resolution.
Is there any way of giving something a prod so that www.icloud.com/photos will realize it only has low-resolution versions of these images and properly acquire the high resolution versions from the phone?
Trying to google the topic mainly just finds lots of people confused by storage optimization and why photos are fuzzy on their device.  But we seem to have the reverse issue of (some) images which are sharp on the device are fuzzy &quot;on iCloud&quot; (or at least when iCloud is viewed via www.icloud.com/photos ).
We have discovered a workround for this issue:

Duplicate the problem image on the phone.
Use &quot;markup&quot; in the photos app to make some miniscule invisible change.  e.g a one-pixel black dot with a semi-transparent pen in some shadowed (but not completely black) region.
Save the modified image.
Wait a couple of minutes and the duplicated image appears on www.icloud.com/photos and is the full resolution version, as expected.

It's worth mentioning that just duplicating the image alone doesn't work: the duplicate will appear on the icloud web-page, but still be fuzzy low-resolution.  Also, modifying the duplicate using other editing controls like exposure, warmth, tint and so on isn't enough of a change to force the upload of a full resolution version, presumably because those parameters are held separately to the original image data (so repeated tweaking doesn't degrade the image).  My guess is modifying the actual image pixel data changes some hash value computed for the image and convinces iCloud there's something needing uploading.
It's a good enough solution for the handful of images we want to see properly uploaded at full resolution.
The most slightly annoying thing about it is that, while the duplicated and modified photos still seem to have the original date attached, www.icloud.com/photos now displays them at the end of the album and unlike the phone app there's no sort options provided.  Not a big deal though, as her main reason for using the iCloud website is just to download images to the desktop PC.