Finder Thumbnails on Exporting HEIC images

[John Perry]

Odd thing seemed to happen today. I exported about a dozen photos from Nitro to a folder as HEIC10 images. When I went to Finder not all the files had thumbnails, but some did. Thought I had done something stupid, exported again, same thing happened, same files without thumbnails. The files open OK and seem fine apart from the lack of a Finder thumbnail.

I then exported as jpegs and all the Finder thumbnails were fine.

It got weirder as I added the meta data I wanted to and imported them into Photos. I then shared the set by using an iCloud Link. I checked that it worked in Safari, clicked download for one of the files, and it still didn’t have a Finder thumbnail. So it seems whatever the problem is, it is persistent…

This has only happened with Nitro, but is it a Nitro problem? I don’t know. Any thoughts?
John Perry

[Nik Bhatt]

Apps can choose to store a thumbnail or not when making files. If no thumbnail is stored, then the Finder will usually make one on its own if it’s a format that the OS understands. I’ll make a note to try to reproduce it, but the fact that it only gets a thumbnail occasionally is odd.

[John Perry]

Thank you Nik, for the reply. Just a couple of points;

1. There is consistency in that exported files that have no Finder thumbnail always have no thumbnail after repeated exports, and those that behave, consistently export with Finder thumbnails.

2. The problem appears with HEIF10; but both JPEG and HEIF8 export with Finder thumbnails.

3. All the files in Nitro are from scanned B&W prints and stored as 16bit greyscale TIFFs from which I am exporting processed versions.

(I have come back to this today, after rebooting my Mac and I am seeing what I saw yesterday… )

Best wishes,
John Perry

[Nik Bhatt]

I looked into this some more – Nitro does request that a thumbnail be inserted into the file during export. I used ExifTool to look for thumbnail data but I only found it for JPEGs, not for HEIF8 or HEIF10. Then I exported a new image using Preview, using HEIF and also did not get a thumbnail (according to ExifTool at least). So, it may be a bug in the OS.

[John Perry]

Tx for looking into it, Nik

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