Monterey 12.6 Preview app cannot open bitmaps!

I'm also facing the same issue since updating to macOS 12.6.

The phenomenon was seen on my three Macs, so I don't think it's a model-dependent problem.

Quick Look can't show the contents of an image, so the Finder only shows an image icon.

Is this a bug? or specification change?

I have same problem. The critical issue is not only Preview app can't open BMP file, but also other apps like (sketch, powerpoint etc) can't import the BMP files. it worked in macOS 12.5.1. if I using opencv read the BMP file then write BMP, it can be opened.

This appears to have been introduced in the latest Monterey update. Previously I could open 1 bit BMP files in Preview and display them via Quicklook. I've tried the files on an older OS and they do not generate errors. Apple need to fix this issue.

I'm glad I checked, as I thought my files were corrupt, but thankfully they weren't. They open fine in Photoshop.

After spending several hours on chat and phone support this afternoon, the final Senior Advisor consulted with "Media Creation" and was told that they were surprised to hear that any version of Monterey had displayed <24bit images in FInder or Preview. It was clear that this issue was a feature, not a bug. That is, Apple intended to drop support of <24bit images. But wait, there's more. When I mentioned to the Senior Advisor that my laptop was telling me that the 12.6.1 update was available but I'd not installed it in the middle of trying to resolve the BMP issue, he suggested I go ahead and install it, because it might very well help. I suspect it was more of a "it couldn't make it worse" suggestion. Anyway, I did the 12.6.1 update and after the reboot, my 8bit BMP images are viewable with Finder, Preview, and a third party app, Pixea, none of which were displaying these images 2 hours ago..

So I have no idea whether Apple intended to drop support for <24bit images, released a bug in 12.6 (ish), doesn't bother keeping its support staff informed, or all of the above, but 8bit BMPs are now working on my MacBook Pro (M1) with 12.6.1. Probably lose it again when 12.6.2 is issued...

Anyone know how this is playing out in Ventura?

Yes, dialabrain, that is what I said. <24 bits means less than 24 bits... Apple support today (10/26/22) told me that bitmaps less than 24 bits should not have been working on any version of Monterey, so they were surprised when I said they were viewable until 12.6. As of 12.6.1, bitmaps of less than 24 bits are working again. No one seems to know what's going on. I also asked the Senior Advisor what the situation was with Ventura and no one could answer that either. The fact that Apple Support was so clueless was disturbing.

I know. I was just repeating what I had said earlier. I wouldn't be too disturbed about what people at Apple Support know or don't know. They have different levels of experience and areas of knowledge. I can't imagine anyone would have total knowledge of all aspects of macOS.

Try the demo version of GraphicConverter. It can handle many, many formats.

FWIW, there appears to be a fix in the next version of Monterey.

1bit, 4bit & 8Bit .bmps.

mareich wrote:

I also asked the Senior Advisor what the situation was with Ventura and no one could answer that either.

FWIW, Ventura supports 8bit bmp files.

FWIW, XnView MP will open bmp files less than 24bit. It's also free.

https://www.xnview.com/en/

I have the same issue on my MacBook Pro. There is also a related problem: SAFARI can not show the similar BMP files, that are able to be shown by iPhone SAFARI.

FWIW, it seems to be an issue introduced with Monterey 12.6. They open before that, and as it turns out, they open in the upcoming Ventura. Whether there's a fix in the works for Monterey is unknown.

I have no idea what you were told. Monterey 12.6 had no problems opening 24bit bmp files. It was bmp files less than 24bits that were a problem which was resolved with 12.6.1.

Just to add, until your post, I hadn't had any reason to work with bmp files in over a decade. I had to find a few online just to test.