Rewrote imgconvert use quantization so we have dithering support

[DavyLandman]

The old code would convert to grayscale, and then chop of the lower 4 bits of the color. This new code allows you to dither, and leave the color mapping to PILLOW/PIL's quantize, which uses a more fancy algorithm where possible.

Some example images (zoom in to see the dithering)

For example, this input:

Used to be turned into:

But now is turned into:

Or less syntatic, this picture:

used to become:

is now:

[martinberlin]

Looks good to me. Will try it soon.
Also assigned CoPilot to review your change so you can check what it says. Just a test if doesn't come out anything good then we just close it.

[DavyLandman]

I don't interact with GenAI, if it helps you manage the OSS project, you do you. Human questions I'm always happy to answer.

I'll try to include a image example of the effect of this PR.

[Copilot]

Pull request overview

This PR modernizes the image conversion script to use PIL's quantization algorithm instead of simple bit-chopping, enabling dithering support for improved grayscale conversion quality.

• Replaces manual grayscale bit-truncation with PIL's quantize method using Floyd-Steinberg dithering
• Adds command-line options to control dithering (-nd flag) and gray levels (-l parameter)
• Updates byte packing logic to work with quantized palette indices

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 9 comments.

File	Description
scripts/imgconvert.py	Implements quantization-based grayscale conversion with palette generation, adds new CLI arguments, and updates pixel packing logic to use palette indices instead of bit-shifted values
scripts/README.md	Documents the new -nd (disable dithering) and -l (gray levels) command-line arguments

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[martinberlin]

Please check the comments and correct what you think is necessary. After that the PR will be approved. Thanks

[DavyLandman]

I've process the remarks, and added screenshots

[martinberlin]

All good

[vroland]

Thanks for implementing this!