And the Prefernces > File Handling > File Saving Options > Image Previews settings have no effect?
...To render a image thumbnail it shows the generic lines of type if layered (useless)...
Can you please be more specific about what "it" is in this context?
What process / application are you using to create these thumbnails?
Here are two screen captures that show what the "it" is when I'm referring to the generic lines of type that Photoshop uses for a thumbnail on a layered document.
"It" refers to the thumbnail that the Mac OS generates or shows in the "preview" in the finder. Don't know that the OS generates the thumbnail or just uses what Photoshop provides. First screen capture is from the DAM library I'm using. The second is from the Mac finder window.
Photoshop Pref > File Handling > File Saving Options is set to:
Image Previews: Always Save, Icon, Windows Thumbnail
Which is why I'm surprised that I don't get an image thumbnail (not the generic lines on a layered file).
What's the purpose of this setting if not to generate a thumbnail of the image.
I'm pretty sure it's the Mac OS that generates Finder thumbnails.
From what I gather, what you're asking for is a thumbnail generation process in the OS that takes into account the Photoshop layered document format and generates proper composited thumbnails for files not saved with the Maximize Compatibility option.
That's not trivial to implement, though I do know that on the PC side codec makers like the folks that make the FastPictureViewer Codec Pack have managed to do it.
This may be normal and expected for the Mac operating system.
that's what I'm guessing. I know that the OS will show an image thumbnail if the Maximize Compatibility option is set to yes. Photoshop then creates a flattened version of the layered psd and includes it in the file data, that's what the OS uses. If the composite info is not available all you get is the generic lines of type. As I said: useless. The DAM (Digital Asset Management) system that I'm using also appears to pull the useless lines of type if a composite image data is not available. The big But.... is the fact that when you select the Maximize Compatibility, the file size balloons by 35% to 88%!! . When you talking about hundreds or thousands of files on a hard drive, that's a lot of additional storage space just to show a image thumbnail.
Not being a coder and therefore I maybe speaking foolishness, I would think that Adobe would have (by now) written code to create a small compressed jpeg to add to the data for the thumbnail. They could leave the full size composite for what is intended (to be compatible with older versions of Photoshop).
I was hoping there was a solution that I wasn't aware of.
The wording in Preferences > File Handling may have misled you. It says "Image Previews" in connection with creating a file icon despite a file's icon having nothing to do with Finder's preview.
With OS X Photoshop, as long as the preference to create icon is enabled, an icon is generated from the visible composite of the document and is attached to the PSD file (not actually embedded in the file) regardless of the Maximum Compatibility setting. Finder will display the icon.
However, Max Compat has to be enabled for a composite to be stored in the PSD, and it is that composite which Finder reads to generate its preview.
At least that's the case for 8-bit per channel PSD.