On Sat, 9 Sep 2017, Henning Hraban Ramm wrote:

> Ahoi,
> I got some long images that I’d like to split over several pages.
>
> \def\clipfigure{\dodoubleempty\doClipFigure}
> \def\doClipFigure[#1][#2]{
>  \dorecurse{#1}{%
>   \clip[
>     height=\textheight,
>     voffset=\dimexpr((\recurselevel -1) * \textheight)
>    ]{\externalfigure[#2][width=\textwidth]}\par
>  }
> }
>
> \clipfigure[3][verylongimage]
>
> But "\dimexpr((\recurselevel -1) * \textheight)" for the vertical offset is wrong.
> How can I do this calculation?

You are missing a comma at the end of the voffset line but why not use
\clip[nx= .., ny=.., x=, y=...] instead.

http://wiki.contextgarden.net/Using_Graphics#Image_Clipping

Aditya