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How do you encode your paper scans? (lemmy.ml)
submitted 1 year ago by Atemu@lemmy.ml to c/selfhosted@lemmy.world
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I assume many of you host a DMS such as Paperless and use it to organise the dead trees you still receive in the snail mail for some reason in the year of the lord 2023.

How do you encode your scans? JPEG is pretty meh for text even at better quantisation levels ("dirty" artefacts everywhere) and PNGs are quite large. More modern formats don't go into a PDF, which means multiple pages aren't possible (at least not in Paperless).

Discussion on GH: https://github.com/paperless-ngx/paperless-ngx/discussions/3756

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[-] Saigonauticon@voltage.vn 5 points 1 year ago

I use JPEGs in a PDF. They can be mediocre quality. Using an OK scanner makes a big difference. It's good enough!

I'm required by law to keep physical paper copies for 35 years. So my parallel solution is a cursed filing cabinet, and several crates that describe the content of the filing cabinet. Its ugly, but saves me tons on data archiving, I guess?

[-] loug@lemmy.ca 2 points 1 year ago

Paperless has a tracking method for paper copies as well; i think the idea is you assign an archive number, then file it in the expected place (for example, 2023-01 to 2023-500 would be one of the 500 docs you get a year, then you put it in the filing cabinet in order from 1 to 500 under 2023). Then you can still search for document by name tag correspondent etc. in paperless and find the archive number.

[-] Atemu@lemmy.ml 1 points 1 year ago* (last edited 1 year ago)

Using an OK scanner makes a big difference.

WDYM? The lossless scans SANE produces themselves subjectively look very good. My only issue is the transcoding to lossy formats I want to do in order to save >3/4 of the space.

[-] Saigonauticon@voltage.vn 1 points 1 year ago

Oh, it's common in my country to use a smartphone to 'scan' documents by actually just taking a lousy photo of them. It's so prevalent that when you tell someone to do a scan they usually do this instead.

I bought a cheap canon scanner for 50$ and it's pretty perfect for legal documents. A little slow maybe. I use SANE, then do lossy compression too.

In rare situations I'd then post process the PDF to even worse quality using ghostscript, for example when a foreign visa application form requires a scan of a really long document, but doesn't accept sizes over 2MB.

[-] sifrmoja@mastodon.social 1 points 1 year ago

@Saigonauticon @Atemu A scanner is a camera. Why complicate things?

[-] Atemu@lemmy.ml 1 points 1 year ago

I use SANE, then do lossy compression too.

Well, what kind of lossy compression? JPEG?

IME, JPEG looks quite terrible for text documents -even at q=95.

[-] dpflug@hachyderm.io 1 points 1 year ago

@Atemu
I just use grayscale PNGs, myself. optipng usually takes them down to a decent size.
@Saigonauticon

[-] Atemu@lemmy.ml 1 points 1 year ago

Hmm, I'm using grayscale PNGs as my baseline here. A 150dpi scan is about 1.3MiB.

A (for the purpose of text documents) similar quality WEBP is about 1/4 of that.

[-] kyle@infosec.pub 1 points 1 year ago

You could also try adjusting the contrast a bit. I use an app called Genius Scan, which increases the contrast of the scanned image to reduce the number of bits needed per pixel. This reduces the size of the file quite a bit, although it obviously isn't a true representation of the scanned document. The TextCleaner imagemagick plugin looks like it's doing something similar.

[-] dpflug@hachyderm.io -1 points 1 year ago

@Atemu
Webp is much better, as long as your target reader(s) support it.

[-] Atemu@lemmy.ml 1 points 1 year ago

Yes, as I said.

As also mentioned in the post, I need a solution for multiple pages and an image (no matter what format) only represents a single page and WEBPs don't go into PDFs.

[-] dpflug@hachyderm.io 0 points 1 year ago

@Atemu
There's not really a magic bullet here. The current answer is to prepare a PDF outside of paperless and feed it in: https://github.com/paperless-ngx/paperless-ngx/discussions/367

mpflanzer on that Issue is working on a file merging feature, but it's not ready yet.

[-] Atemu@lemmy.ml 1 points 1 year ago

That's nice and all but does not answer how you'd create the PDF. Whether that happens outside paperless inside paperless does not make a difference. In the end, I need to create a PDF/A out of some images and the question on how to encode these images still remains.

[-] Saigonauticon@voltage.vn 1 points 1 year ago

Yeah just jpeg. Always comes out perfectly legible.

[-] kyle@infosec.pub 3 points 1 year ago* (last edited 1 year ago)

I’ve never used paperless but just checked it out and it looks pretty neat. My first thought would be to scan documents in a higher resolution, let the OCR happen, then convert the file to a JPEG or something smaller after you’ve extracted the text.

I spent a few minutes looking at their wiki and it looks like it might be possible.

Like I said though, no experience with this software so I’m not sure that’d actually work.

[-] Atemu@lemmy.ml 4 points 1 year ago

Interesting idea but I think I'd like to retain similar to original quality in case I wanted to redo OCR if/when Paperless' OCR improves in the future.

[-] surewhynotlem@lemmy.world 1 points 8 months ago

By 'paperless', y'all mean this one? https://docs.paperless-ngx.com/

[-] Atemu@lemmy.ml 2 points 8 months ago

Correct. That's the currently maintained paperless project.

[-] surewhynotlem@lemmy.world 2 points 8 months ago

Thanks! There's a very interesting trail of dead projects to follow. But I got ngx working and it's great so far.

[-] Atemu@lemmy.ml 1 points 8 months ago

I for one am still waiting for paperless-ngnxn2-next-3.0_hypr.

[-] flux@lemmy.ml 2 points 1 year ago

There is the DJVU format for this exact use case, but you'd need to convert them to, say, pdf for many use case. Its also a bit old and perhaps not maintained, soo..

HEIF and other modern video encoders (HEIF=H265) should fare a lot better than JPEG, though.

[-] Atemu@lemmy.ml 1 points 1 year ago

Hm, DJVU seems like an ancient format and it also only supports JPEG and J2K as far as lossy formats go.

I'd love to use more modern formats such as AVIF, HEIF or even WEBP but paperless doesn't support some of them and images in general can only represent one page while many of my scans have multiple pages.

[-] lemming007@lemm.ee 0 points 1 year ago

PDF/A

[-] Atemu@lemmy.ml 1 points 1 year ago

And how do you encode the images of the scan contained in the PDF/A? That's the crux here.

[-] lemming007@lemm.ee 1 points 1 year ago

I'm not sure I understand. I just scan anything and let my software spit out PDF/A

[-] Atemu@lemmy.ml 1 points 1 year ago

PDF/A is not an image format. As a document, it may contain images.

[-] lemming007@lemm.ee 1 points 1 year ago* (last edited 1 year ago)

My PDF/A documents contain all kinds of content, including text and images. To me, it doesn't matter what format the encoded images are, as long as I can open them 20 years from now. Why would one care one way or another?

[-] Atemu@lemmy.ml 1 points 1 year ago

I care that the text remains readable (both to me and also software) and that I don't balloon my storage out of control.

JPEG (even at higher levels) subjectively degrades text in particular to a degree that I worry about the former and PNG makes me worry about the latter.

My current plan is to go with the latter since storage is a relatively cheap issue to fix while data loss is pretty much permanent.

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this post was submitted on 07 Jul 2023
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