Help- Artifacts/Corruption in several Photos

I have the same issues. Been searching for something on this. Glad I found this thread. I seemed to notice the artifacts occur on photos taken from my wife’s iPhone 7 and copied into my photos library. The thumbnail (or photo placeholder shows the artifacts), then when I zoom (causing the photo to download from the cloud) the artifacts disappear. I use my late 2012 iMac to copy her files (from a Dropbox folder) into my master iCloud library. The files are saved as HEIC. They aren’t edited by software but are copies of the original (Live feature doesn’t copy) so they may be similar to edited photos. On my iMac running Mojave they look fine (I don’t optimize for space), but the previews on my iPhone X and on my appletv 4K show the artifacts. iPhone 7 doesn’t show artifacts (photo unedited on this device). iPad Air 2 shows artifacts. Would love to hear if a solution is discovered beside converting files to different formats.

iMac (27-inch, late 2012)

Processor 2.9 GHz intel core i5

Memory 24 GB 1600 MHz DDR3

Graphics NVIDIA GeForce GTX 660M 512 MB

iPhone X 256 GB

iPhone 7 256 GB

AppleTV 4K

iPad Air 2

"me too". The irregular banding (moiré) is not present on original photos (several hundred) taken with our iPhone Xs (x3), nor is it present on our iCloud synced iPads - it is only present in Mojave Photos app and only in the photos (most but not all) imported after upgrading to Mojave. Exporting and converting files from HEIC to JPG directly from the Photos app does not clear the artifact. Likewise, exporting and converting files from HEIC to JPG using Preview was not successful - the moiré persists.

james from peachtree city wrote:

... Likewise, exporting and converting files from HEIC to JPG using Preview was not successful - the moiré persists.

That's very interesting and different than our results, are you sure you are saving as JPG? when you re-open the photo check its type by displaying Info.

Thanks for your reply. I eventually found that using the Photos Export command and then using Preview to convert from HEIC to JPG was unnecessary. Instead I created a folder on the Desktop and click/dragged the hundreds of artifact affected photos from the Mojave Photos app to the newly created Desktop folder - that action alone converted the HEIC files to JPG without resorting to Preview. The converted JPG photos were indeed artifact fee. Subsequently I used a folder action to rename the new JPG photos as the Photos app would not have otherwise allowed re-importation, having identified the photos as already existing in the app's catalog. I choose to use Find & Replace in the following manner: Find "." & replace with "-2.", resulting in the following naming format "IMG-1149-2.jpg”. Of course I now have duplicates and can safely delete the HEIC artifact files as I choose.

When you drag the photos to the Desktop, they may be in a lesser quality than the originals, because dragging will just save the JPEG previews. with exporting you will have more control over the quality.

I have this very same issue with my photos taken on both iPhone 7 Plus and iPhone Xs Max when viewed on iMac 27" Late 2012 with macOS Mojave 10.14 and 10.14.1 installed. I'm strongly convinced this has something to do with the new HEIF and its support on older Macs without HEVC hardware-accelerated decoding.

I agree it’s hardware/software related. But not because the iMac is missing decoding hardware. The issue was not present in High Sierra. I believe this is Metal 2 related. I don’t have this issue in Preview app, most likely because it’s still running on Open GL. QuickView and Photos are both affected by the artifacting issue with HEIC.

Preview is iffy, sometimes the artifacts show, sometimes they don't. Whats worse if you print a HEIC photo looking ok in Preview, you get the darn artifacts in the print. I was hoping Apple would fix something in the latest 10.14.1 but alas no ...

I took a radical approach and switched to using RAW (DNG) on the iPhoneX, sure it takes 3x as much as a HEIC photo, but it beats buying a new iMac!

Have the images showing up bad in Preview been edited on your iMac? Or are they originals untouched? Once you edit HEIC on the affected Computer with the artifacts it will then be backed into the image and show up everywhere including iOS devices. In my experience, exporting the Original HEIC and opening in Preview has never exhibited this issue.

Luckily my 2016 MacBook can edit them so I just made a smart album for HEIC images. I’ve since switched my iPhone to shoot JPG.

Indeed, unedited HEIC photos taken on iPhoneX and sent to my iMac show artifacts in Preview or quick preview. But sometimes once the image is opened in Preview the artifacts disappear. You go figure...

I am more and more convinced that this problem is specific to certain iMac models from around 2013.

I am not seeing this problem on my MacBook Pros in Photos 4.0 on Mojave, but two days ago I took the plunge and upgraded my iMac as well to Mojave. And now I am seeing corrupted thumbnails and artifacts for the heic images, not only the images from my iPhone X, but also the images I converted to HEIC on my MacBook pros. My iMac is an iMac 27", late 2013.

Exporting to a different image format (I tried TIFF) there are no artifacts

That seems to be a feasible workaround while we are waiting for an official release with a fix -for this bug - export all HEIC images as TIFF. Have you tested this with several corrupted images?

Yes I have, in fact all 53 HEIC images I took yesterdag exported fine to TIFF without any artifacts.

I don't believe the images are really corrupted as they show up fine in Photos while using HEIC and can be exported to other formats than JPG. It has to do with conversion from HEIC to JPG on Mac and previewing HEIC images with Quick Look.

When I drag an image from Photos to Finder now, it converts to .jpeg without artifacts. So I guess maybe yesterday the images weren't fully downloaded from iCloud (missing hi res preview?). When I browse images in Photos on Mac I see the artifacts for a short time and then they disappear. One image which I edited does have the artifacts.

Yes, the images themselves seem to be fine. My HEIC files are syncing with iCloud Photos between three different Macs, and I can view then without problems in my Mac Book Pros, it is just the 2013 iMac with the older Graphics card, that is having trouble to generate JPEGs from the HEIC images.

Ok this is getting more weird. Now a TIFF won't export without artifacts.

When I preview an image in Photos (double click an image), first I see the artifacts for fraction of a second, then they disappear.

When I drag an image from Photos to Finder which I have not previewed in Photos before, the artifacts show up.