How to draw a double-color line with tikz

Question

I would like to draw a rectangle with a double color border: the border should be a line dashed with two alternating colors (blue and red, for example). Is it possible?

Related question: Two color line in gnuplot. The basic idea is to draw the line twice. Once solid with one color then dashed with the second one. — Martin Scharrer, Apr 17 '11 at 19:35
Thank you. I don't know how to equally divide the space (actually, I am using geogebra to generate the rectangle: how can I specify the parameters of the dashed line?) — zar, Apr 17 '11 at 19:56
For tikz you can define a dash pattern using e.g. dash pattern=on 2pt off 2pt. No idea how to handle geogebra here. — Martin Scharrer, Apr 17 '11 at 20:04

Frédéric · Accepted Answer · 2011-04-17T20:54:06.993

30

As mentionned in Martin's comment, the trick is to draw the line twice. One of the constraints on paths in Tikz/PGF is that the color is global to the path.

Other than drawing a solid line covered by a dashed line, you may draw two dashed lines, with spaces between the dashes, as given by the following example (you can find more information in the Tikz manual) :

\begin{tikzpicture}

\draw[blue,dash pattern= on 3pt off 5pt] (0,0) |- (1,1) to[out=0,in=90] (2,0);
\draw[red,dash pattern= on 3pt off 5pt,dash phase=4pt] (0,0) |- (1,1) to[out=0,in=90] (2,0);

\end{tikzpicture}

The outcome is

two color dashed line

(Following a comment by Caramdir) : The same result can be achieved with a postaction, and the path only has to be specified once :

\draw[postaction={draw,red,dash pattern= on 3pt off 5pt,dash phase=4pt,thick}]
[blue,dash pattern= on 3pt off 5pt,thick] (0,0) |- (1,1) to[out=0,in=90] (2,0);

(Following a request for a rectangle) * I'm not sure this answers the question in the comment *

For a rectangle you would type in the command

\draw[postaction={draw,red,dash pattern= on 3pt off 5pt,dash phase=4pt,thick}]
    [blue,dash pattern= on 3pt off 5pt,thick] (0,0) rectangle (3,2);

This rectangle does not have rounded corners, it is a "normal" rectangle. If ever you do want rounded corners, add rounded corners to the options :

\draw[postaction={draw,red,dash pattern= on 3pt off 5pt,dash phase=4pt,thick,rounded corners}]
    [blue,dash pattern= on 3pt off 5pt,thick,rounded corners] (0,0) rectangle (3,2);

edited Apr 17 '11 at 20:54

answered Apr 17 '11 at 20:01

Frédéric

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Nice! You could even use three or more colors using this technique. – Martin Scharrer Apr 17 '11 at 20:05
5

For more complicated paths, it might be more convenient to use a postaction, so that the path doesn't need to be specified twice. – Caramdir Apr 17 '11 at 20:05
Good! One last thing: how can I draw a "good" rectangle with this tecnique? I would like to have rounded corners, but now rounded dashes. – zar Apr 17 '11 at 20:14
I'm not sure what you mean about a good rectangle, with rounded corners and now [to you mean not] rounded dashes. – Frédéric Apr 17 '11 at 20:21
Sorry, "not" rounded dashes. – zar Apr 17 '11 at 20:34
Like this one: [http://img863.imageshack.us/i/notgood.png/] – zar Apr 17 '11 at 20:37
@zar : see the addition to my answer – Frédéric Apr 17 '11 at 20:50

score 5 · Answer 2 · answered Dec 10 '23 at 17:09

In case you want to have a double colored border around a node, you can do it like this:

\documentclass{standalone}
\usepackage{tikz}
\begin{document}
    \begin{tikzpicture}
        \node[circle,draw=blue,dash pattern= on 3pt off 5pt,thick,postaction={draw,red,dash pattern= on 3pt off 5pt,dash phase=4pt,thick}] at (0,0) {TEST};
    \end{tikzpicture}
\end{document}

How to draw a double-color line with tikz

2 Answers2

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