Recasting a 32-bit image in 8-bits, 4 bits, and 1 bit

Talk about Pixelmator Pro, share tips & tricks, tutorials, and other resources.
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2021-04-23 03:53:24

Here's a weird request: many years ago, I wanted to communicate to a class the increase in verisimilitude that larger words give a computer. I started with a nice photograph. Then I used a photo manipulation program (Adobe Photoshop? I can't remember) to create an 8-bit version, a 4-bit version, and a 1-bit version. When I was done, I had four images: a nice full-color image, a rather clumsy image with only 256 colors, an even clumsier image with just 16 colors, and a black and white image (no grayscale: all pixels either black or white).

I would like to repeat that trick for a new lecture I'm preparing, but I can't find any program that does what I need. Perhaps the problem is simply that I don't know the correct terminology to describe the process. Perhaps, if I just did a search for "frambobulation", say, I'd find it easily, but I'm too ignorant to know that.

When I asked about this at a Mac forum, they had no idea of what I was talking about; perhaps this makes no sense to you, either. If not, I'll try to explain it in more detail. I have played around with Pixelmator Pro trying to accomplish this, but I have not been successful. Part of the problem, I suspect, is that images are no longer stored with color index tables, making this kind of thing impossible. Still, I think that, in programming terms, this could all be accomplished by simply masking out the lower bits in a standard 32-bit pixel representation.

Can anybody suggest how I might accomplish this with Pixelmator Pro, or some other program?
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2021-04-26 10:17:14

Hey there Chris. I think I pretty much understand what you're getting at. If you're only looking to do this for illustrative purposes, you could try applying the Posterize effect (in the Stylize effects category) to your image. With Posterize, you can choose the exact number of colors you want in your image. This essentially means that 2 levels of colors would be equal to 1-bit and 16 levels to 4-bit images. For an 8-bit image, select the 8-bit option from the Color Depth menu (Image > Color Depth). Hope that helps!
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2021-04-26 14:49:27

Yes, that solves my problem! Thank you so much! I was sure that there was something in Pixelmator Pro that could do it -- there are so many special effects, it just HAD to be in there somewhere, but somehow I did not stumble upon it.

Thanks again!
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2021-04-28 07:22:48

Awesome. I wasn't sure if that was exactly what you're looking for but I'm glad it helped!