Skip to content

Instantly share code, notes, and snippets.

Last active July 9, 2024 16:43
Show Gist options
  • Save andyrbell/25c8632e15d17c83a54602f6acde2724 to your computer and use it in GitHub Desktop.
Save andyrbell/25c8632e15d17c83a54602f6acde2724 to your computer and use it in GitHub Desktop.
Make a pdf look scanned using ImageMagick
# use ImageMagick convert
# the order is important. the density argument applies to input.pdf and resize and rotate to output.pdf
convert -density 90 input.pdf -rotate 0.5 -attenuate 0.2 +noise Multiplicative -colorspace Gray output.pdf
Copy link

Seem to have solved it (slowing making as I write) with Homebrew/legacy-homebrew#6103 (comment) for each and every invalid cert.

Do think there must be a way to update my machine's certs so that curl can work correctly though.

Copy link

@turkeyphant: Well, if these SSL errors are not only related to curl then something is really off. Sometimes an utterly wrong system time causes such errors (because the certificates seem to be expired/not valid yet) or you're in a shitty corporate network that uses some kind of HTTPS-Interception and thus breaks security or you're the victim of a MITM attack.

Copy link

turkeyphant commented Jun 12, 2020

It's seems to be a common macos issue to be honest. System time is correct, there is no vpn or other network issues and I'm fairly certain there's no mitm going on (have tested various Internet connections for example and other macos machines). It's 10.11 and the certificates might just be out of date?

Copy link

DavidWuthier commented Oct 5, 2020

Nice! The other day, I had 19 pages to sign with unique signatures. First, I used xournal on Ubuntu 20.04 with a stylus, and then I ran the following script:

#!/usr/bin/env bash

# Dependencies
sudo apt install pdftk imagemagick -y

# Output folder
mkdir -p output

# Keep pages in the right order
for i in {1..19}; do
  if (( $i < 10 )); then

  pdftk input.pdf cat $i output output/$j.pdf
  convert -density 200 -trim -flatten -quality 80 -attenuate 0.15 +noise Multiplicative -rotate 0.01 output/$j.pdf output/$j.jpg
  convert output/$j.jpg output/$j.pdf
  rm output/$j.jpg

pdftk output/* cat output result.pdf

The conversion to .jpg prevents the file from bloating.

Copy link

The +noise Multiplicative argument created a dappled background behind where I had text but not in other places. Using Gaussian, Laplacian, or Uniform instead of Multiplicative produced better results for me.

Copy link

dazhbog commented Dec 2, 2020

If you get this error:

convert-im6.q16: not authorized `input.pdf' @ error/constitute.c/ReadImage/412.
convert-im6.q16: no images defined `output.pdf' @ error/convert.c/ConvertImageCommand/3258.

you can run

sudo mv /etc/ImageMagick-6/policy.xml /etc/ImageMagick-6/

to disable the policy. When done, you can restore the original with

sudo mv /etc/ImageMagick-6/ /etc/ImageMagick-6/policy.xml

Taken from here

Copy link

Guys - completely newbie here
I downloaded Visual studio and Git as per install-windows.txt
then ... how do I run the file?
Do I add this file into folder somewhere...?

tks .....

Copy link

Pezmc commented Feb 17, 2021

I've improved upon this script slightly (having used it for a while now):

  • by splitting the PDF into separate pages per file
  • applying slightly different rotations to each page
  • recombining the files
  • support for macOS automator quick actions
  • Fixing the noise so it appears across the document


Copy link

vwkd commented Sep 24, 2021

Thanks @Pezmc. To have the noise only at the edges instead of across the whole document is a feature IMO, and also keeps the file size much smaller. Unfortunately, I couldn't figure out how to get your script to use noise only at the edges.

I ended up modifyng the original script using the higher density to make the output sharper. Got to keep up with the increasing quality of the scanners in the 3 years since then. 😉

convert -density 130 input.pdf -rotate 0.2 -attenuate 0.2 +noise Multiplicative -colorspace Gray output.pdf

Copy link

For those on Windows make sure to install Ghostscript as well or else you'll get errors like

convert: FailedToExecuteCommand `"gswin32c.exe" -q -dQUIET -dSAFER -dBATCH -dNOPAUSE -dNOPROMPT -dMaxBitmap=500000000 -dAlignToPixels=0 -dGridFitTT=2 "-sDEVICE=pngalpha" -dTextAlphaBits=4 -dGraphicsAlphaBits=4 "-r150x150"  "-sOutputFile=C:/Users/TURKEY~1/AppData/Local/Temp/magick-9420wtSmlrXSBcfh%d" "-fC:/Users/TURKEY~1/AppData/Local/Temp/magick-9420IJ2RKxHzcTQf" "-fC:/Users/TURKEY~1/AppData/Local/Temp/magick-9420t7VINjcK97Pq"' (The system cannot find the file specified.
) @ error/delegate.c/ExternalDelegateCommand/475.
convert: PDFDelegateFailed `The system cannot find the file specified.
' @ error/pdf.c/ReadPDFImage/662.

Copy link

restyler commented Jan 3, 2022

thank you! I have used some of these commands to build which not only applies scanner effect, but also allows to insert an image of signature or draw a signature.
My observations regarding -density parameter: 200 is good enough in most cases, while 300 gives ultimate quality - but the build time get catastrophically slow..

Copy link


Copy link

fewaltix commented Mar 16, 2022

Thank you!
I used zenity to add graphical input and output prompts:
convert -density 150 "$(zenity --file-selection --title="Select Input File" --file-filter=*[PpDdFf])" -rotate "$([ $((RANDOM % 2)) -eq 1 ] && echo -)0.$(($RANDOM % 4 + 5))" -attenuate 0.4 +noise Multiplicative -attenuate 0.03 +noise Multiplicative -sharpen 0x1.0 -colorspace Gray "$(zenity --file-selection --save --title="Select Output File" --filename ".pdf")"

Can also be found here as a .desktop file, so the script can be started from the starter on Linux machines:

Copy link


Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment