139
edits
Changes
Jump to navigation
Jump to search
< [[Using–Graphics]] >__NOTOC__
== Measures in pure ConTeXt ==
adding "Measures in Lua"
If you’re using ConTeXt for complex layout tasks, you need to calculate with image sizes. Often it makes sense to use Lua functions.
'''Beware''', TeX calculates internally in "scaled points" (sp), 1 sp = 1/65536 pt.
You can get at a picture’s dimensions with one line of TeX code:
\stoptabulate
</context>
= Measures in Lua =
There is a way to take them in Lua:
<context source="yes">
\setupexternalfigures[location=default]
\setupbodyfont[sans, 20pt]
\starttext
\startTEXpage[offset=1em]
\startluacode
local f = figures.getinfo("cow.pdf")
context(f.used.width)
context.par()
context(f.used.height)
context.getfiguredimensions({ "cow.pdf" })
context.par()
context(context.noffigurepages)
context.par()
context(context.figurewidth)
context.par()
context(context.figureheight)
\stopluacode
\stopTEXpage
\stoptext
</context>
The <code>figures.getinfo</code> gives just numbers and it has less options. <code>context.getfiguredimensions</code> gives the same outputs than it TeX counterpart.
= Calculations in Lua =
<pre>
TEXpt = 65536 -- sp per pt
TEXptpi = 72.27 -- pt per inch
function sp2mm(n)
-- convert sp into mm
return math.floor(n * 35.28 / TEXpt)/100
end
function glue2num(glue)
-- convert TeX glue (e.g. skips) into dimensions(? or numbers)
return glue.width + (glue.stretch * glue.stretch_order) - (glue.shrink * glue.shrink_order)
end
function ImgSize(resolution)
local filename = figures.current().status.fullname -- current image
local pic = img.scan{filename = filename}
local picH = pic.ysize * TEXptpi * TEXpt / resolution -- picture height in sp
local picW = pic.xsize * TEXptpi * TEXpt / resolution -- picture width in sp
context("height=" .. picH .. ",width=" .. picW)
end
</pre>
= Postponing =
If you want to place full page images or similar content on distinct pages, try the postponing mechanism:
<texcode>
\definemakeup[fullpage][
page=no,
doublesided=no,
% headerstate=empty,
% footerstate=empty,
pagestate=start,
]
\startpostponing[pagenumber]
\startfullpagemakeup
% use \setlayer & friends
\stopfullpagemakeup
\stoppostponing
</texcode>
The pagenumber argument can be absolute or relative, e.g. 23 or +2. Values like +0 or -1 might fit your usecase.
((WORK IN PROGRESS))
[[Category:Graphics]]
