How can I compress in terms of pixels not file size?

Started 2 months ago | Questions thread
OP CameronCox New Member • Posts: 3
Re: Very specific suggestion

Thank you for your detailed insights (and patience! )

What you have touched on all makes sense and yes I agree 4-bits per colour channel produces some pretty gnarly images. This is for research to do with a much larger project started long before I joined it and since it is a camera destined for a small Low Earth Orbit satellite I'm guessing the numbers have already been crunched and there must be a good rationale behind why we're going with 12-bit per pixel rather than 24-bit.

After further digging around, I think the file type I'm trying to extrapolate back to is an uncompressed bitmap (BMP).

I understand that the raw file is not what I thought it was, but still, even if I had a highly (losslessly) compressed PNG, x pixels wide, y pixels tall, each of those pixels must be a certain colour when the image is viewed, so surely you could 'uncompress' this image to its pure data form which would be 'pixel one is colour 'a' defined by this 12-bit number, pixel two is colour 'b' defined by this other 12-bit number' and so on, so that this file's size in bits would be the product of number of pixels and pixel bit depth?

(It's an odd idea that you could go from a smaller to larger file size theoretically this way. Unless, of course, it's completely impossible in practice; sort of like violating the first law of thermodynamics?)

Applied to the 954x954 image referred to earlier, there would be 910,116 pixels, with 12 bits (1.5 Bytes) each to give an overall 'uncompressed' file size of 1.365MB (also assuming we're using the 1,000 per size step, not 1,024)

I understand that using such an unwieldy, large file is odd, but I'm just trying to get a file that I can use to simulate how our camera and on-board-computer might go about performing its compression regimes and I'd rather not 'feed' a pre-compressed image into that simulation.

I apologise if I've just come full circle again and asked the same question but I think this might be a slightly different track I'm on now?

Again thanks for the terrific help!

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