cswita wrote:
MacOS Finder does not generate image previews for files with more than 21 Alpha Channels.
What's an "alpha channel" (plural)? That must be a Photoshop thing like layers. I can pretty much tell you now that it's a Photoshop problem.
Save the image in .tif, .psb, or .psd format with "Maximize PSD and PSB File Compatibility" enabled in Adobe Photoshop (for greatest file compatibility; though this doesn't impact results).
It would be better to use only TIF images for issues like this. All bets are off for proprietary image formats like PSD. I know you said it happens with TIF images, but you only posted PSD examples. Since that's a proprietary format, a logical assumption is that only Photoshop fully supports these files.
MacOS should generate and display an image preview/thumbnail regardless of the number of Alpha Channels.
Here's the problem. PSD is a proprietary image format. Apple generally only provides Quicklook preview for common image formats. PSD is one of the outliers. It used to be more common, which is why Apple has support for it in the first place. There are many similar threads regarding EPS files after Apple completely removed support from EPS from the operating system.
For whatever reason, Apple still has some PSD support. But I'm sure this is very old. I don't know when Adobe added this concept of multiple alpha channels, but Apple's PSD support probably pre-dates that. That's why you don't see them and won't ever see them.
Finder does not generate an image preview for images with more than 21 Alpha Channels.
Finder doesn't generate any image previews. It is the responsibility of an app to generate QuickLook previews for the documents it supports. Apple does provides some QuickLook generators for very common file formats. But those are subject to Apple's whims (like EPS) or to Apple's lack of interest in proprietary formats (PSD, RAW, etc.) Maybe PSD is one of those. I don't know.
For example, when I downloaded your examples, it is Pixelmator Pro that manages the QuickLook previews on my computer. I see the same problem that you describe, I guess. Obviously only one file has a valid preview. The most likely explanation is that Apple's ancient PSD logic doesn't fully support this format. Obviously Apple's built-in QuickLook preview is going to use Apple's logic. Apparently Pixelmator Pro uses Apple's logic too.
An important point here is that I don't know what app is providing the previews for PSD files on your computer. One would assume that Photoshop does this. But I realize that Photoshop has every poor Mac support. Adobe users are constantly complaining in these forums about Adobe bugs and limitations. Apparently Adobe just blames their own failures on Apple and sends people to this forum so they don't have to deal with their own unhappy customers. So perhaps Adobe doesn't provide any Quicklook previews at all. (I've noticed how Adobe used to have beautiful icons years ago and now they're just squares with letters. It makes sense that they couldn't manage a decent preview.)
• The `qlmanage` command hangs when attempting to generate previews for these images.
Just so you know, Apple's procedures for generating these previews has radically changes over the past decade or so. qlmanage may be hacked up enough to still provide some functionality. But that's one of the reasons why you don't see so many previews anymore. None the preview apps from years ago will run any more. It's a long story.
Any insights or solutions to ensure image previews are generated correctly in the Finder for images with more than 21 alpha channels would be greatly appreciated.
Ask Adobe to properly support their own image formats on the Mac. I realize that's a futile effort.
no other application allows you to save in Photoshop's .psd or .psb format so I'm not following what application you would propose other than Photoshop.app to create those files?
Actually Preview can export in PSD format if you hold down the option key. Not sure how long that support will last. It will definitely last the weekend. Not sure about Monday. 😄
The same issue occurs with QuickLook
To clarify, all of this is QuickLook. There are two kinds of QuickLook generators - previews and icons.
This is just a really basic problem with popular files formats. Adobe wants everyone to use Adobe products so they publish formats for "compatibility". Apple et al. add support for PSD and PDF. Then Adobe goes crazy adding new features to PSD and PDF. Apple can't keep up. Yes, it's Apple's fault for falling for it. But now Apple has enough customers and money not to care.
