MWE (compiles with XeLaTeX):
\documentclass{tufte-book}
\usepackage{xcolor}
\definecolor{PrussianBlue}{cmyk}{1,.41,0,.67}
\usepackage{geometry}
\usepackage{scalerel,scalefnt}
\usepackage[LGR,T1]{fontenc}
\newcommand{\textgreek}[1]{\begingroup\fontencoding{LGR}\selectfont#1\endgroup}
\usepackage[greek,english]{babel}
\usepackage{substitutefont}
\substitutefont{LGR}{\rmdefault}{artemisia}
\usepackage{tikz}
\usetikzlibrary{decorations.text}
\tikzset{mydecor/.style 2 args={decoration={text along path,
text align={left indent=2em},
text={|\bfseries\huge|#2},
},
yshift=#1,
decorate}}
\begin{document}
\thispagestyle{empty}
\begin{tikzpicture}
\fill[PrussianBlue] (-6,0) rectangle (6,9) (180:0.45cm) arc (180:360:0.45cm);
\draw[line width=0.3cm,PrussianBlue!45,fill=white,miter limit=1]
(0,0.45) to[controls={+(150:2.25cm) and +(25:2.25cm)}] (-5.4,0.6) --
(-5.4,9.6) to[controls={+(25:2.25cm) and +(150:2.25cm)}]
(0,9) to[controls={+(30:2.25cm) and +(155:2.25cm)}] (5.4,9.6) --
(5.4,0.6) to[controls={+(155:2.25cm) and +(30:2.25cm)}]
(0,0.45) -- (0,9);
% Left page
\path[mydecor={-8ex}{How to type}] (-5.4,9.6) to[controls={+(25:2.25cm) and +(150:2.25cm)}] (0,9);
\path[mydecor={-9.5ex-2\baselineskip}{Capital BETA,}] (-5.4,9.6) to[controls={+(25:2.25cm) and +(150:2.25cm)}] (0,9);
\path[mydecor={-11ex-4\baselineskip}{To take up the}] (-5.4,9.6) to[controls={+(25:2.25cm) and +(150:2.25cm)}] (0,9);
\path[mydecor={-12.5ex-6\baselineskip}{Entire page?}] (-5.4,9.6) to[controls={+(25:2.25cm) and +(150:2.25cm)}] (0,9);
\end{tikzpicture}
\end{document}
with output
I would like to type, for example, a capitalized (bold) Beta that I may scale (say, using \scalefnt) to fit the entire left page of this open TikZ book.
I have tried using the \textgreek and \scalefont commands, as usual, around the text---but that doesn't work. Nor have I been able to successfully modify text={|\bfseries\huge|#2}, either to get the task accomplished.
QUESTION: How may I incorporate, say, \textgreek{B} and the \scalefont command so that a capitalized and bold (arched) Beta take up most of the left-hand page of the displayed open book?
Thank you.


text effects along pathis more flexible, though I believe a bit slower. However, it won't allow you to curve a character. For that you'd need to convert the character to a path. If you really need that, maybemetapostwould be a better choice. – cfr Jan 15 '24 at 04:36