Knowledge Base (Posts about pdf)

Convert pdf to jpg

bgstack15 — Wed, 18 Dec 2024 13:58:00 GMT

Quick and dirty, but way better than convert input.pdf output.jpg. I'm assuming there was a resolution setting somewhere for "convert" that I never bothered to research.

pdftoppm -jpeg -r 300 input.pdf output

Specifically omit the extension, because you will get files like output-1.jpg, output-2.jpg, et al.: one for each page.

References

Ripped shamelessly from:

How to convert a PDF into JPG with command line in Linux? - Stack Overflow

Extract attached file from encrypted PDF

bgstack15 — Sat, 20 Jul 2024 12:54:00 GMT

I received an email with an attached pdf. This pdf was password-protected (encrypted). Atril thankfully can read those, but I didn't know how to view the file attached to the pdf. (Yes, I know, attached inside an attachment; I wasn't in control of the sender.)

Besides, who wants to use a graphical environment when a cli will do?

qpdf input.pdf output.pdf --decrypt --password='passphrasehere'
mkdir -p outdir
pdftk output.pdf unpack_files output outdir

Old research

My old solution involved pdftk and pdfdetach and for some reason I was failing to read the pdf correctly with pdftk.

pdftk inputfile.pdf input_pw 'passphrasehere' outputfile.pdf
pdfdetach -upw 'passphrasehere' -saveall inputfile.pdf

References

Split a pdf

bgstack15 — Wed, 02 Feb 2022 13:59:53 GMT

Just like combining pdfs, you can use pdftk to extract certain pages.

pdftk in.pdf cat 1 3-5 11 output out.pdf

From two files:

# Extract pages 1-3 from first and 6-10 from second file
pdftk A=first.pdf B=second.pdf cat A1-3 B6-10 output out.pdf

References

Weblinks

Ripped directly from Code Yarns – How to extract pages from PDF using PDFTK

My scanpdf solution

bgstack15 — Tue, 25 Jan 2022 14:15:58 GMT

I have not personally needed to forcibly scan a document, i.e., print one out, just to sign it, and then scan it in again. I have my trusty signatures.pdf that I scanned in a few years ago with 10 iterations of my signature. I always just screenshot a signature, and use LibreOffice Draw's ability to set a transparent color of an imported image.

But, after reading an interesting Hacker News discussion, I have whipped up a "scanpdf" solution. 99% of this is ripped straight from the author, mrb.

Here is my file ~/bin/scanpdf.sh, with typo/semantic fixes.

	`#!/bin/bash`
	`# from https://news.ycombinator.com/item?id=30024165#30027344`
	`# Make a pdf look like it was scanned.`

	`if [ $# -ne 2 ]; then`
	`echo "Usage: $0 input output" >&2`
	`exit 1`
	`fi`
	`tmp="$1".scanner-look.tmp`
	`mkdir "$tmp" &&`
	`# without -flatten some PDF convert to a JPG with a black background`
	`convert -density 150 "$1" -colorspace Gray -quality 60 -alpha flatten "$tmp"/p_in.jpg &&`
	`: \|\| exit 1`
	`# each page is randomly shifted in the X and Y plane.`
	`# units seem to depend on angle of rotation in ScaleRotateTranslate?`
	`offset() { echo $(($RANDOM % 1000)); }`
	`for f in "$tmp"/p_in*jpg; do`
	`# each page is randomly rotated by [-0.5 .. 0.5[ degrees`
	`angle=$(python3 -c 'import random; print(random.random()-0.5)')`
	`x=$(offset)`
	`y=$(offset)`
	`convert "$f" \`
	`-blur 0x0.5 \`
	`-distort ScaleRotateTranslate "$x,$y $angle" +repage \`
	`$ +clone +noise Random -fill white -colorize 95% $ \`
	`-compose darken \`
	`-composite \`
	`${f/p_in/p_out}.pdf \|\| exit 1`
	`done`
	`# concatenate all the pages to one PDF`
	`# use "ls -v" to order files correctly (p_out-X.jpg where X is 0 1 2 ... 9 10 11 ...)`
	`pdftk $(ls -v "$tmp"/p_out*.pdf) cat output "$2" &&`
	`rm -rf "$tmp"`

Dependencies include pkdftk(1) and ImageMagick. Also important is to make sure the ImageMagick policy had read and write acess to PDFs. Ensure something similar to this logic is in file /etc/ImageMagick-6/policy.xml.

<policy domain="coder" rights="read | write" pattern="PDF" />

References

Weblinks

Combine pdfs

bgstack15 — Sat, 03 Jul 2021 13:26:21 GMT

I remember needing to combine PDFs in the past, even on GNU/Linux, but I forgot how I did it back then. The first search result for query combine pdfs linux I found said to use ImageMagick! I keep that around for all sorts of tasks already, so:

convert file1.pdf file2.pdf mergedfile.pdf

But the quality was terrible. I didn't want to bother with dealing with quality settings in ImageMagick, when I remembered there was something out there that would work. It was farther down in that first result: just use pdftk.

pdftk file1.pdf file2.pdf cat output mergedfile.pdf

I'm not sure why this is so hard for the Internet.

Bonus

Also, LibreOffice draw struggles with pdfs that have fonts that are not on your system. You can achieve limited success by using mutool extract from package mupdf-tools. Unfortunately for me, the font name used didn't match up with the ttf font name properties because of the whole "FontName-Bold" stuff. So I still had to manually munge stuff, and apparently some of the embedded glyphs were not included so it took some playing around with manually changing a random letter "V" into the non-bold version to get it to appear. That was frustrating. And I had gotten so far as to use ttx filename.ttf from package fonttols but didn't get any farther in that experiment.