3

What is a small piece ot tikz code for reproducing the figure below ?

enter image description here

Source: http://withits.epfl.ch/_media/events/slides-elgamal.pdf

Notes: I'm familiar with this question Draw a $\epsilon$ neighborhood, but it doesn't really answer my quest.

5

Welcome to TeX.SE! EDIT: Adjusted the tension parameter to get a smoother output.

\documentclass[tikz,border=3.14mm]{standalone}
\begin{document}
\begin{tikzpicture}
 \draw[double distance=6pt,fill=blue] plot[smooth cycle,tension=0.7] coordinates {(0,0) (0.3,0.6) (1,0.8) (1.4,0.2)
 (1.2,-0.3) (0.4,-0.4)};
 \draw[latex-] (3pt,0) -- ++(-1,-0.2) node[left]{$\mathcal{A}$};
 \draw[latex-] (1.4cm+3pt,0.2) -- ++(1,-0.2)
 node[right]{$\Gamma_\ell(\mathcal{A})$};
\end{tikzpicture}
\end{document}

enter image description here

This animation shows a bit what tension does.

\documentclass[tikz,border=3.14mm]{standalone}
\begin{document}
\foreach \X in {0.5,0.6,...,1.5}
{\begin{tikzpicture}
 \draw[double distance=6pt,fill=blue] plot[smooth cycle,tension=\X] coordinates {(0,0) (0.3,0.6) (1,0.8) (1.4,0.2)
 (1.2,-0.3) (0.4,-0.4)};
 \draw[latex-] (3pt,0) -- ++(-1,-0.2) node[left]{$\mathcal{A}$};
 \draw[latex-] (1.4cm+3pt,0.2) -- ++(1,-0.2)
 node[right]{$\Gamma_\ell(\mathcal{A})$};
\end{tikzpicture}}
\end{document}

enter image description here

Of course, you can also adjust the coordinates.

4

You can simply start by drawing a triangle like \draw (1,0)--(-2,3)--(2,5)--cycle, then, with the aid of a grid you start adding two control points between each pair of vertices like .. controls (a) and (b)... You need to tweak the control points a bit to get the desired shape. Look at this answer, e.g., to know more about how to choose control points.

\documentclass[tikz,border=5pt]{standalone}
\usetikzlibrary{arrows.meta}
\begin{document}

\begin{tikzpicture}[scale=.5, > = Stealth] 
 \draw[double distance=10pt,fill=blue] (1,0)  .. controls (-1.5,0) and (-2.5,2)..
                                       (-2,3) .. controls (-1,5)   and (1,5.3) ..
                                       (2,5)  .. controls (5,4)    and (3,0)   .. 
                                       (1,0)  -- cycle;
 \draw[<-] (-1.5,1.5) -- ++(-1,-0.2) node[left]{$\mathcal{A}$};
 \draw[<-] (3.5,1.5)  -- ++(1,-0.2)  node[right]{$\Gamma_\ell(\mathcal{A})$};
\end{tikzpicture}

\end{document}

enter image description here

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.