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title: "Obtaining Cropped Line Drawings From Simulink"
date: 2018-10-12T13:38:23Z
draft: false
category: guide
excerpt: "Guide for turning sprawling Simulink diagrams into crisp vector figures by printing to PDF, splitting with pdftk, and batch-cropping with pdfcrop. I finish with a shell script that automates the entire workflow."
- ---

# Diagrams, Diagrams Everywhere

## Motivation

For my third year project I needed a way to put my ~wave:annoyingly large~ Simulink system into a document.
Screenshots won't do because the quality is far too low :myeyes:, so I generally avoid putting raster images in reports.
There clearly had to be a better way, which I hope show in this short but useful post.
These methods will work with MacOS and \*nix systems.

At the end of the post is a tool which will give you the ability to split and crop a multi page pdf all in one go, with some basic usage directions.

## Get the PDF

This part is simple enough, press 'print' and a dialog box will pop up.
Select 'print to file' and 'all systems', as highlighted in the image below:

![Printing](print.png)

This should print a PDF file to some location specified on your system.
This is fantastic! We have a line drawing representation of our diagram, albeit in a rather unusable form, we clearly need to split this file up and deal with it more from there.

## Split the PDF

Fortunately we do not have to get too involved with PDF reading, as a tool exists to help us with PDF mainpulation!

We can use _pdftk_ to split our multi-page PDF into single page PDFs by executing the following command:

```bash
pdftk multipage.pdf burst
```

You may have to install _pdftk_, as it is not guaranteed as standard on \*nix.

I really like _pdftk_, it gives you more tools for PDF manipulation than you would ever need, and it's free software!

Here is a little aside where I (actually pulled from help files) list some of the answers to the question: _What can you do with pdftk?_

1. Merge PDF Documents

- - Split PDF Pages into a New Document
- - Rotate PDF Pages or Documents
- - Decrypt Input as Necessary (Password Required)
- - Encrypt Output as Desired
- - Fill PDF Forms with FDF Data or XFDF Data and/or Flatten Forms
- - Apply a Background Watermark or a Foreground Stamp
- - Report on PDF Metrics such as Metadata, Bookmarks, and Page Labels
- - Update PDF Metadata
- - Attach Files to PDF Pages or the PDF Document
- - Unpack PDF Attachments
- - Burst a PDF Document into Single Pages
- - Uncompress and Re-Compress Page Streams
- - Repair Corrupted PDF (Where Possible)

## Crop the PDFs

Again the great UNIX gods pity us, another tool exists which allows us to crop PDF documents!

The tool in question (a perl script!) is the appropriately-named _pdfcrop_, which comes pre-installed on MacOS and \*nix systems.

To use _pdfcrop_, perform the following command:

```bash
pdfcrop singlepage.pdf
```

_pdfcrop_ will then output a file called `singlepage-crop.pdf` in the same directory.

Which when put together should give you a nicely cropped simulink line drawing!

## Automating ourselves out of the job

Splitting and cropping that PDF was honestly a very involved process.
_pdfcrop_ has to be called for each page, and the number of files involved becomes a small nightmare, especially if you make changes to your plant and need to update your diagrams.

Fortunately I have taken the liberty in writing a small bash script, which can be used as following (after a `chmod +x splitcrop.sh`).

```bash
./splitcrop.sh multipage.pdf
```

For my Third Year project I ended up using this script, but with some commands to automatically rename the files taked onto the end, here's one for example:

```bash
mv ./split_files/pg_0001-crop.pdf ../report/3yp_general/images/plant/Global.pdf
```

This may be useful if working with a group project and making lots of small changes, otherwise omit this.

## Splitcrop.sh

```bash
#!bin/env/bash

echo "Splitting PDF $1"

# split the pdf and move all pages to a `split files' folder

pdftk $1 burst
mkdir split_files
mv pg_0\* ./split_files/

filetype=".pdf"
files=`find ./split_files/`

# crop each pdf

for file in $files
do
    if [[ $file = *${filetype} ]]; then
        echo "Splitting $file"
        pdfcrop $file
    fi
done

# remove non-cropped files

mv ./split*files/*-crop.pdf ./
rm ./split*files/*
mv \*-crop.pdf ./split_files/
```
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