Reduce colour depth option and compression option

[NextTherapist]

Is your feature request related to a problem? Please describe. I would like to be able to reduce colour depth in NAPS2 after scanning or importing a colour or greyscale image or PDF, before generating a PDF file.

Describe the solution you'd like An option to choose the target colour depth and a preview to judge if these settings lead to a readable result. And then deciding which compression should be used, JPG or CCITT.

Best case would be a new option to use JBIG2 compression optionally.

[cubed-it]

I have a large number of color scans of documents that should actually be saved in black and white. I'm missing a function like this, especially via the cli.