Package: diff-pdf-visually
Table of ContentsHow to install thisOn Ubuntu LinuxOn Mac with Homebrew (untested)On Windows Subsystem for LinuxOn Windows nativeHow it worksSo what do you use this for?StatusSupported Python versionsThis script checks whether two PDFs are visually the same. So:White text on a white background will beignored.Subtle changes in position, size, or color of text will bedetected.This program will ignore changes caused by a different version of the PDF generator, or by invisible changes in the source document.This is in contrast to most other tools, which tend to extract the text stream out of a PDF, and then diff those texts. Such tools include:pdf-diffby Joshua TaubererThere seem to be some tools similar to the one you’re looking at now, although I have experience with none of these:Václav Slavík seems to havean open source oneThere might be more useful ones mentioned onthis SuperUser threadThe strength of this script is that it’s simple to use on the command line, and it’s easy to reuse in scripts:fromdiff_pdf_visuallyimportpdf_similar# Returns True or Falsepdf_similar("a.pdf","b.pdf")Or use it from the command line:$pip3install--userdiff-pdf-visually$diff-pdf-visuallya.pdfb.pdfHow to install thisYou can install this tool withpip3, but we need the ImageMagick and Poppler programs.On Ubuntu Linuxsudo apt updatesudo apt installpython3-pipimagemagickpoppler-utilspip3 install--userdiff-pdf-visuallyIf this is the first time that youpip3 install--usersomething, then log out totally from Linux and log in again. (This is to refresh thePATH.)Run withdiff-pdf-visually.On Mac with Homebrew (untested)Runbrew install poppler imagemagick.pip3 install--userdiff-pdf-visuallyIf this is the first time that youpip3 install--usersomething, then close your terminal and open a new one. (This is to refresh thePATH.)Run withdiff-pdf-visually.On Windows Subsystem for LinuxI’ve never tried but I think this will work. Give it a go and let me know (at bram at bram dot xyz) if it worked! Unfortunately it takes quite a while to get everything installed.Install Windows Subsystem for Linux (WSL) and Ubuntu 18.04, for instancewith this tutorialInitialize Ubuntu 18.04 (tutorial)Now proceed with the Ubuntu Linux instructions.Let me know (at bram at bram dot xyz) if this worked!On Windows nativeLars Olafsson suggested that the following might work:Installdiff-pdf-visuallyvia Pip.Install ImageMagick, e.g. viahttps://imagemagick.org/script/download.phpDownload pdftocairo/Poppler, e.g. the old Windows build produced by Todd Hubers and Ilya Kitaev:https://blog.alivate.com.au/poppler-windows/. Extract the .7z file somewhere and update the WindowsPathvariable to add thebinfolder that was extracted.Rundiff-pdf-visually.How it worksWe usepdftocairoto convert both PDFs to a series of PNG images in a temporary directory. The number of pages and the dimensions of the page must be exactly the same. Then we callcomparefrom ImageMagick to check how similar they are; if one of the pages compares different above a certain threshold, then the PDFs are reported as different, otherwise they are reported the same.You must have ImageMagick and poppler already installed.Calldiff-pdf-visuallywithout parameters (or runpython3-mdiff_pdf_visually) to see its command line arguments. Import it asdiff_pdf_visuallyto use its functions from Python.There are some options that you can use either from the command line or from Python:$ diff-pdf-visually  -h
usage: diff-pdf-visually [-h] [--silent] [--verbose] [--threshold THRESHOLD]
                         [--dpi DPI] [--time TIME]
                         a.pdf b.pdf

Compare two PDFs visually. The exit code is 0 if they are the same, and 2 if
there are significant differences.

positional arguments:
  a.pdf
  b.pdf

optional arguments:
  -h, --help            show this help message and exit
  --silent, -q          silence output (can be used only once)
  --verbose, -v         show more information (can be used 2 times)
  --threshold THRESHOLD
                        PSNR threshold to consider a change significant,
                        higher is more sensitive (default: 100)
  --dpi DPI             resolution for the rasterised files (default: 50)
  --time TIME           number of seconds to wait before discarding temporary
                        files, or 0 to immediately discardThese “temporary files” include a PNG image of where any differences are, per page, as well as the log output of ImageMagick. If you want to get a feeling for thresholds, there are some example PDFs in thetests/directory.There is also an environment variable:COMPARE: override the path of ImageMagick compare. By default, we try firstcompareand thenmagick compare(for Windows).So what do you use this for?Personally, I’ve used this a couple of times to refactor my LaTeX documents: I just simplify or remove some macro definitions, and if nothing changes, apparently it’s safe to make that change.StatusAt the moment, this program/module works best for findingwhethertwo PDFs are visually different.This project will not work on Python 2.The code is dual-licenced under bothMIT LicenseApache License, Version 2.0at your option.Supported Python versionsThe versions that are regularly tested can be foundhere, that’s probably Python 3.8 and Python 3.9.For your convenience we declare more Python versions acceptable inpyproject.toml, but the non-tested versions could potentially break from time to time. My goal is to support basically Python 3.x; please let me know if something doesn’t work on an older version.