Re: automatically splitting big images (calculation problem)

[Henning Hraban Ramm <texml@fiee.net>]

Am 2017-09-09 um 22:06 schrieb Aditya Mahajan <adityam@umich.edu>:

> 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

Thank you, but that’s not the core problem.
I get "Illegal unit of measure (pt inserted)".


My current code actually looks like

% split in #1 page size parts
\def\clipfigure{\dodoubleempty\doClipFigure}
\def\doClipFigure[#1][#2]{
\ifsecondargument
  \dorecurse{#1}{%
  \tooltip{\clip[
    height=\textheight,
    voffset=\dimexpr((\recurselevel - 1)\textheight),]{%
    \externalfigure[#2]}}{#2 (\recurselevel/#1)}\par}
\else
  \normalfigure[#1]
\fi
}


Another approach:

\def\ausschnitt{\dodoubleempty\doAusschnitt}
\def\doAusschnitt#1#2{\clip[height=\textheight,voffset=#1]{\externalfigure[#2][width=\textwidth]}\par}

This also doesn’t work; there I’m trying to set the y coordinate for the start like
\ausschnitt[15cm][verylongimage]

Here I get "Missing number, treated as zero".


I guess I need to employ the right combination of \the, expansion etc., but I don’t know how. This stuff is still over my head.


> but why not use
> \clip[nx= .., ny=.., x=, y=...] instead.
> http://wiki.contextgarden.net/Using_Graphics#Image_Clipping

Because I don’t want to split the picture in even slices, but cut in places where it makes sense. The page height is a simplification, until I get the calculations working.


BTW example picture:
http://www.balderdashcomic.com/comic/ibonus
i.e. http://www.balderdashcomic.com/comics/1416175460-bonus1.png


Greetlings, Hraban
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