Re: Let chapter start on odd page and make the even page before show an image

[Wolfgang Schuster <wolfgang.schuster.lists@gmail.com>]

Jan U. Hasecke schrieb am 29.05.2020 um 15:10:
> Am 29.05.20 um 12:45 schrieb Wolfgang Schuster:
>> juh schrieb am 29.05.2020 um 10:29:
>>> Dear all,
>>>
>>> with your help I can colorize the empty even page right before a
>>> chapter starts
>>> on the odd page. The mwe below shows it.
>>>
>>> Now I would like to redefine the contents of the left page on the fly
>>> in the text
>>> so that I could place images on this page.
>>>
>>> I thought that I could get a simple solution by inserting a TEXpage as
>>> even
>>> page, but this does not work for several reasons. First a TEXpage is
>>> not counted
>>> correctly like a normal page.  And secondly I found now way to put it
>>> on the
>>> even page.
>>>
>>> So what I really want to achieve is a way to redefine this setups at
>>> some point
>>> in the text to insert eg. a picture on the even page before a chapter.
>>>
>>> \startsetups [chapter:before]
>>>     \doifoddpageelse
>>>       {}
>>>       {\pushbackground[page]
>>>        \setupbackgrounds[page][background=color,backgroundcolor=blue,]
>>>        \page[empty,right]
>>>        \popbackground}
>>> \stopsetups
>>>
>>> As you see the image is not in the right place and of course the
>>> pagenumbering
>>> is wrong.
>> Use \startTEXpage[pagestate=start] to increase the page number with TEX
>> pages.
> Thanks for this hint.
>
>>> I want that one of these blue pages shows an image. Is this possible?
>> Yes but there are different ways for different requirements.
>>
>> - Do you you have a picture before *every* chapter?
> No, the additional image page shall appear only if the last chapter ends
> on an odd page. Then I need the image page to push the new chapter to
> the next odd page.
>
>> - Do you use full page images?
>> - Are the images cropped to fit the page dimension, stretched or
>> centered with margins?
> For this usecase images are blown up and cropped to fit the page
> dimension including the bleed.

\setuppagenumbering
   [alternative=doublesided]

\setupexternalfigures
   [location=default]

\definedataset [chapter]

\startsetups [chapter:before]

   \page[yes]

   \doglobal\increment\ChapterCounter

   \doifoddpageelse
     {}
     {\doifsomething
        {\datasetvariable{chapter}{\ChapterCounter}{image}}
        {\startlayout[page]
         \centerbox{\externalfigure
[\datasetvariable{chapter}{\ChapterCounter}{image}][factor=min]}
         \stoplayout}}

\stopsetups

\setuphead
   [chapter]
   [page=,
    beforesection=\directsetup{chapter:before},
insidesection={\setdataset[chapter][\ChapterCounter][image=\structureuservariable{image}]}]

\setupexternalfigure[location=default]

\starttext

\startchapter [title={Tufte}] [image=cow]
\dorecurse{4}{\samplefile{tufte}}
\stopchapter

\startchapter [title={Knuth}] [image=mill]
\dorecurse{8}{\samplefile{knuth}}
\stopchapter

\startchapter [title={Zapf}] [image=hacker]
\dorecurse{6}{\samplefile{zapf}}
\stopchapter

\stoptext

Wolfgang

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