How to Give an Elliptical Border a Braided Effect

Question

Consider the code

\documentclass{book}
\usepackage{graphicx}
\usepackage[abs]{overpic}
\usepackage{tikz}
\definecolor{cadmiumgreen}{rgb}{0.0, 0.42, 0.235} % 0, 107, 60
\definecolor{Gold}{RGB}{228,168,73}

\begin{document}
    \thispagestyle{empty}
    \begin{center}
        \begin{tikzpicture}
            \clip (0,0) ellipse (4.25cm and 5.5cm);
            
            \draw[line width=5pt,Gold,fill=cadmiumgreen!93.5] ellipse (4.25cm and 5.5cm); 
            \node at (0,0) {\includegraphics[scale=.37,clip, trim = 0 0 0 0]{example-image-a}};
            \draw[line width=10.5pt,Gold] ellipse (4.25cm and 5.5cm); 
        \end{tikzpicture}
    \end{center}
\end{document}

which produces the image

QUESTION: I would like to give the gold border a braided effect. Does anyone know how this might be accomplished?

Thank you.

Answer 1

I don't know what you mean by "braided effect". I made a wild guess: something like an old picture frame. But details can be changed...

I define a decoration, mainly, taking two arguments: the number of steps (of the effect) and the width of the line to which the decoration is applied. Both are used as dimensions in points afterwards.

Remark It works better with closed curves.

The code

\documentclass[11pt, border=1cm]{standalone}
\usepackage{tikz}
\usetikzlibrary{math, calc}
\usetikzlibrary{decorations.markings}

\definecolor{CadmiumGreen}{RGB}{0, 107, 60}
\definecolor{Gold}{RGB}{228, 168, 53}
\definecolor{DarkGold}{RGB}{221, 137, 53}
\begin{document}

\tikzset{%
  braid/.style 2 args={% nb of steps, width in pts
    preaction={draw=DarkGold, line width=#2pt},
    decoration={%
      markings,
      mark=between positions 0 and 1 step 1/#1 with {
        \tikzmath{%
          \dl = \pgfdecoratedpathlength/#1;
          {
            \draw[DarkGold, line width=#2/13 pt, fill=Gold,
            rounded corners=5pt, rotate=-40]
            (.4*\dl pt, 0) rectangle ++(.7*\dl pt, .8*#2 pt);
            \draw[DarkGold, line width=#2/10 pt, fill=Gold,
            rounded corners=3pt, rotate=20]
            (0, -.3*#2 pt) rectangle ++(\dl pt -1pt, .7*#2 pt);
          };
        }
      }
    },
    postaction=decorate
  }  
}

\begin{tikzpicture}
  \draw[Gold, fill=CadmiumGreen, line width=10pt, braid={60}{12}]
  ellipse (4.25cm and 5.5cm);
\end{tikzpicture}

\end{document}

Answer 2

\documentclass[tikz, border=1cm]{standalone}
\begin{document}
\begin{tikzpicture}[
line width=8.3pt,
declare function={
rx=4.25;
ry=5.5;
n=10;
da=180/n;
ex1=(rx+0.2*cos(n*\t))*cos(\t);
ey1=(ry+0.2*cos(n*\t))*sin(\t);
ex2=(rx+0.2*cos(n*\t+120))*cos(\t);
ey2=(ry+0.2*cos(n*\t+120))*sin(\t);
ex3=(rx+0.2*cos(n*\t+240))*cos(\t);
ey3=(ry+0.2*cos(n*\t+240))*sin(\t);
},
samples=10, smooth, variable=\t,
]
\fill[teal] ellipse[radius=rx, y radius=ry];
\foreach \i [parse=true] in {0,...,(2*n-1)}{
\draw[orange!95!black] plot[domain=(\i-3/3)*da:(\i+0/3)*da+0.2] (ex1,ey1);
\draw[orange!85!black] plot[domain=(\i-2/3)*da:(\i+1/3)*da+0.2] (ex2,ey2);
\draw[orange!75!black] plot[domain=(\i-1/3)*da:(\i+2/3)*da+0.2] (ex3,ey3);
}
\clip (0,0) rectangle (rx,-ry);
\foreach \i [parse=true] in {(2*n)}{
\draw[orange!95!black] plot[domain=(\i-3/3)*da:(\i+0/3)*da+0.2] (ex1,ey1);
\draw[orange!85!black] plot[domain=(\i-2/3)*da:(\i+1/3)*da+0.2] (ex2,ey2);
\draw[orange!75!black] plot[domain=(\i-1/3)*da:(\i+2/3)*da+0.2] (ex3,ey3);
}
\end{tikzpicture}
\end{document}

Answer 3

Here's an alternative in Metapost using a routine I wrote earlier that draws any path as a rope (sort of).

This is wrapped up in luamplib so you need to compile it with lualatex.

\documentclass[border=5mm]{standalone}
\usepackage{graphicx}
\usepackage{luamplib}
\begin{document}
\mplibtextextlabel{enable}
\begin{mplibcode}
vardef rope expr c =  % c is a circular path...
    save s, w, n, a, b, A; 
    numeric s, w, n, A; 
    w = -1; n = -1; A = arclength c; s = A/floor(A/2);
    path a[]; 
    for t=0 step s until A + 1:
        a[incr n] = (0,+w) rotated angle direction arctime t-3/2s of c of c shifted point arctime t-3/2s of c of c
                 .. (0,+w) rotated angle direction arctime t-1/2s of c of c shifted point arctime t-1/2s of c of c
                 .. (0,-w) rotated angle direction arctime t+1/2s of c of c shifted point arctime t+1/2s of c of c
                 .. (0,-w) rotated angle direction arctime t+3/2s of c of c shifted point arctime t+3/2s of c of c;
    endfor
    image(
        for i=1 upto n:
            path b; b = buildcycle(a[i-1], reverse a[i]);
            fill b withcolor 1/2[white, gold]; 
            draw b withpen pencircle scaled 1/8 withcolor gold;
        endfor
    )
enddef;

color gold, cadium_green; 
gold = 1/256(228, 168, 72);
cadium_green = 1/256(0, 107, 60);

beginfig(1);

    path frame; frame = fullcircle scaled 5cm xscaled 17/22;
    fill frame withcolor cadium_green;
    draw rope frame;
    label("\includegraphics[width=3cm]{example-image-a}", origin);

endfig;
\end{mplibcode}
\end{document}

Adjust the value of w to make the rope thicker, and to flip between cable-laid and hawser-laid. -1 gives you a good looking cable (which is usually used for decoration), 1 gives the other direction. -2 looks a bit fatter.