92 lines
5.4 KiB
Markdown
92 lines
5.4 KiB
Markdown
---
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Title: Block ads using LaTeX
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Date: 2019-04-23 09:00
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Modified: 2019-04-23 14:23
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Author: Fabrice
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Lang: en
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Category: tips
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Tags: LaTeX, inkscape, ads, git
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Slug: latex-ad-block
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og_image: images/thumb_stop-pub.png
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twitter_image: images/thumb_stop-pub.png
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Header_Cover: images/covers/velov.jpg
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Summary: Blocking ads in your print-yourself tickets has never been so easy. A script is available at the end of the article.
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---
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I'm quite annoyed with ads. As of many, I'm using an adblocker on my computer, but there is one kind of ads that annoys me the most: ads on printable ticket. Not only it poisons our eyes, but it consumes ink to print it.
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I'm aware that we can just open the QR/barcode on your smartphone, but still, isn't it better if we can get rid of the ad directly?
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A first obvious solution could be to import your pdf in any [image editing software](https://www.gimp.org/) and simply use any rectangle shape selection tool to remove the ad.
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However, this produces a new pdf file (or image file) that does not contain any more information about the text, and which may grow in size.
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A simple workaround is then to use a vector graphic editor to keep this information: for instance, opening the PDF with [inkscape](https://inkscape.org/), and remove the image corresponding to the ads.
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Yet more elegant, this approach still has a serious drawback: it breaks the fonts. Also, some of them (such as Air France's “_Excellence in Motion_” font) are proprietary and cannot be found easily/legally for free.
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But inkscape can still be of use in order to remove those ads.
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Indeed, it allows finding the coordinates and the dimensions of those ads as illustrated in the following (click to zoom):
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[]({static}/examples/inkscape-adblock.png)
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**Explanations:** After opening your pdf file, start by selecting the ad (<span style="color:#8b0074">purple</span>), you may have to ungroup elements (`ctrl+shift+g`), then set the dimensions in cm or your favourite length unit (<span style="color:#0000ff">blue</span>) and finally note the dimensions of the ad (<span style="color:#ff0000">red</span>).
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Then we just use LaTeX to add a white (or any background color, I let you devise it by yourself, you can use RGB codes with [xcolor](https://www.ctan.org/pkg/xcolor)) rectangle in front of the ad.
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I already used the [wallpaper](https://www.ctan.org/pkg/wallpaper) package in [another post]({filename}latex-letterhead.md), but it has some limitations: it doesn't allow us to import multiple pages (such as a round-trip ticket), and tikz doesn't interact well with the induced page geometry.
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Thus, I used this [answer on stackexchange](https://tex.stackexchange.com/questions/12838/can-i-add-tikzpictures-to-pages-included-with-pdfpages).
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To put it short, we use the package [pdfpages](https://ctan.org/pkg/pdfpages) with its options `pages={-}` to include every page, and the option `pagecommand` to include the rectangle overlay with the right dimensions `X`, `Y`, `L`, `H`.
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That gives us the following `.tex` file which can simply be compiled with your favorite latex typesetter (for instance `pdflatex file.tex` twice).
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```tex
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\documentclass[a4paper]{article}
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% Tikz with pdfpages
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\usepackage{tikz}
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\usetikzlibrary{calc}
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\usepackage{pdfpages}
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% avoid page numbering
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\pagestyle{empty}
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\begin{document}
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\includepdf[pages={-},% include all pages
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pagecommand={% is called at the beginning of each inclusion
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\begin{tikzpicture}[remember picture,overlay]
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\draw[color=white,fill=white] ($(current page.north west) +%
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(X, -Y)$) rectangle ++ (L, -H);%
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\end{tikzpicture}%
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}]%
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{original file.pdf}
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\end{document}
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```
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**Remark:** You may have noticed the minus sign in front of `Y` and `H`. This is because tikz computes coordinates from bottom left of the page, while inkscape (and gimp) starts at top left (and the frame is oriented accordingly).
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Some examples of dimensions to copy-paste (mostly for myself):
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* Rhônexpress:
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```tex
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… + (1.5cm, -14.65cm)$) rectangle ++ (18cm, -9cm);
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```
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* Air France/KLM foldable tickets.
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```tex
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… + (11cm, -18cm)$) rectangle ++ (9cm, -9cm);
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```
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You may have noticed that the dimensions are larger than in the above picture, this is because Air France sometime uses square ads.
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However, if you plan to use your smartphone, these companies also attach an ad-free `png` with minimal information.
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As I don't buy a plane ticket every day, I didn't feel the need to script it, and I don't have enough examples to make an interesting enough database of ad locations.
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However, it is a great opportunity to get some more data about it, therefore there you can `git clone` the script from [here](https://git.epheme.re/fmouhart/hidepdfads).
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As it is a self-hosted private repository, if you are eager to contribute, you may want to do a pull request on its [github repository](https://github.com/Chouhartem/hidepdfads) or send me an email on <img style="height:2em" src="/images/mel.png" alt="courriel"/>. In any case, feel free to contact me for any further remarks, comments or questions.
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<center>
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[XKCD #1319](https://xkcd.com/1319/) by Randall Munroe.
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</center>
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## See also
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* [pdf-adblock](https://github.com/anthony-morel/pdf-adblock) on github.
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It's a script based on heuristics (for instance an ad will be an image) to remove single-page-ads automatically from a PDF (for instance a magazine PDF).
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<!-- vim: spl=en
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-->
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