~~ODT~~
====== fancy way to generate scale bars with Tikz ======
The way to display scale bars shown [[:latex#scale_bars|here]] is nice, but can be a bit cumbersome if the images are not that easy, e.g. the image shows a skewed sample in 3D. Everything shown below could also be done completely by hand, but it's quite a boring task to calculate multiple [[http://www.dict.cc/?s=dreisatz|rules of three]] for every image you want to add a scale bar. I've written a small MATLAB-script to facilitate the calculation and addition to LaTeX.

You'll need:  {{  :latex:tikz:scalebarimage.jpg?128|}}
  * an image you know the scale of and want to draw the scale bar on, e.g. the image shown on the right((it's an MRI of my head...))
  * MATLAB with this m-file: {{:latex:tikz:scalebar.m|}} (or any other graphics-capable calculation program like [[http://www.gnu.org/software/octave/|Octave]])
  * this minimal tex-file: {{:latex:tikz:scalebar.tex|}} (I suppose you have a running installation of LaTeX to work with this example...)
Both files are explained in a bit more detail at the end of this page, for now I'll just walk you through:

===== WorkFlow =====
  - Start MATLAB, load scalebar.m and start it.
  - The script prompts you to load an image, choose "scalebarimage.jpg" you've downloaded from above.
  - The script prompts you to define the length of the scale bar you're gonna draw in the next step, choose the default "21 cm" for now
  - The script displays the image of my head and asks you to define a start-point of the scale-bar, choose the tip of the nose
  - After that, choose the back of my head for the end of the scale-bar
  - Note the "Positions" shown in the help-dialog, these are to make sure you've clicked correctly and that the positions are correct.
  - copy the output in the command-line-section of MATLAB
  - paste this output into your .tex-file
  - if the .tex file and the image are in the same folder, just proceed, if not, change the path to the image!
  - compile the file
  - Figure 1 of the document should show
    * the exact same scale-bar you've drawn in MATLAB overlayed over the image.
    * a second scale bar which shows a reasonable length (5cm in our case){{  :latex:tikz:scalebarfigure.png?256  |}}
  - change \def\x{100} and \def\y{100} on lines 24 and 25 of the copied text to position the scale bar where you'd like to have it and uncomment line 29 to turn off the original scale bar.
  - enjoy typographically correct scale bars in the resulting {{:latex:tikz:scalebar.pdf|pdf}} (47 kB)
  


===== LaTeX-File =====
The preamble is nothing too fancy
<code latex>
\documentclass{article}
\usepackage{tikz}                 % used for actually drawing the scale bar
\usepackage[ansinew]{inputenc}    % is used so I can write my name without too much hassle 
\usepackage{siunitx}              % excellent package to correctly typeset units
\usepackage{hyperref}             % used for URLs
</code>

The block below is used to start the document and to set up the image
<code latex>
\begin{document}
\author{David Haberthür}
\title{David Haberthür's Head - Scalebar}
\date{\today}
\maketitle
\begin{figure}[h]
	\centering
</code>

Inside here you'll copy the result from the MATLAB-skript, the rest ist just to finish off the document.
<code latex>
\caption{Three dimensional visualization of David Haberthürs Head, released under a \href{http://creativecommons.org/licenses/by/2.0/deed.en_GB}{creative commons Attribution 2.0 Generic license} by the owner of the head.}
	\label{fig:head}
\end{figure}
\end{document}
</code>

===== MATLAB-File =====

The block below asks the user to select an image-file that is then subsequently used for calculations
<code matlab>
[ filename, pathname] = ...
     uigetfile({'*.jpg;*.tif;*.png;*.gif','All Image Files';...
          '*.*','All Files' },'Choose Input Image');

image=imread([pathname filesep filename]);
</code>

The scale bar is defined by asking the user to click on the image for a start- and end-point.
<code matlab>
h = helpdlg('choose start-point of scale bar','ScaleBar');
uiwait(h);
[ x1,y1 ] = ginput(1);
</code>
the rest is just simple, but boring calculations and semi-nice output, which takes care of setting up the necessary lengths for TikZ.

===== References =====
TikZ: http://kogs-www.informatik.uni-hamburg.de/~meine/tikz/\\
MATLAB: http://blinkdagger.com/matlab/matlab-querying-the-user-for-input