Also you can use this:

assuming that you have a fixed size figure such as a pdf page:

\definesymbol[Bsymbol][{\scale[width=1.6ex]{\externalfigure[myfile.pdf][page=1]}}]
\define\mysym{\kern 0.2em \symbol[Bsymbol] \kern 0.3em}

\starttext
this is a sample\mysym text.
\tfa{this is a sample\mysym text.}
\stoptext

On Mon, Jun 10, 2024 at 7:18 AM Gerion Entrup <gerion.entrup@flump.de>
wrote:

> Hi,
>
> I'd like to scale something (actually a symbol drawn in TikZ) to the exact
> high of the char 'M'. I found the scale environment for it but struggle to
> measure the correct font height. I found the
> "definemeasure/measure/measured"
> commands but they define a dimension and are not for doing measurements on
> rendered text. Is there a simple way to get the height a char as a
> dimension?
>
> MWE:
> ```
> \starttext
> % Is it possible to replace 1cm with a common expression?
> This is the letter M. \scale[height=1cm]{a} should have the exact same
> size as
> M.
>
> This should also be true {\tfc with a bigger M. \scale[height=1cm]{a}}.
> \stoptext
> ```
>
> Best
> Gerion
>
>
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