mjhjmtu

The following code gives extra space both on the left under the graphic and on the right under the text. Is there a way to make the split rectangles tight against the larger text or graphic?

% !TEX encoding = UTF-8 Unicode
% !TEX TS-program = XeLaTeX

documentclassarticle

usepackagegraphicx
usepackagetikz
usepackagemulticol

usetikzlibraryshapes.multipart,positioning

newsaveboxtestbox

begindocument

beginlrboxtestbox
 beginminipage3in
 beginmulticols2
 This is a lot of bla bla bla to see what is happening. And this is more text. and a lot more. And this is more text. and a lot more. And this is more text. and a lot more. 
 endmulticols
 And this is more text. and a lot more. And this is more text. and a lot more. And this is more text. and a lot more
 endminipage
endlrbox

tikz%
 node[%
 rectangle split,
 rectangle split parts=2,
 rectangle split horizontal,
 rectangle split part align=top,
 draw,
 line width=3pt
 ](test)%
 includegraphics[width=2in]example-image-a
 nodeparttwo useboxtestbox.
 ;
 node[above=12pt of test.south,fill=white]%
 bfseriesLARGEcolorred $Longleftarrow$ EXTRA SPACE? $Longrightarrow$;
%

enddocument

This has to do with the way you include the graphics. Here is one out of many ways to fix it: put it in $vcenterhbox...$, which is a standard trick to vertically center objects (in equations). My choice is not special, nor sophisticated, but seems to work. As for the question: why is this necessary here? I do not have a compelling answer except maybe that I am not surprised to have to care about the vertical alignment.

documentclassarticle

usepackagegraphicx
usepackagetikz
usepackagemulticol

usetikzlibraryshapes.multipart,positioning

newsaveboxtestbox

begindocument

beginlrboxtestbox
 beginminipage3in
 beginmulticols2
 This is a lot of bla bla bla to see what is happening. And this is more text. and a lot more. And this is more text. and a lot more. And this is more text. and a lot more. 
 endmulticols
 And this is more text. and a lot more. And this is more text. and a lot more. And this is more text. and a lot more
 endminipage
endlrbox

tikz%
 node[%
 rectangle split,
 rectangle split parts=2,
 rectangle split horizontal,
 rectangle split part align=top,
 draw,
 line width=3pt
 ](test)%
 $vcenterhboxincludegraphics[width=2in]example-image-a$
 nodeparttwo useboxtestbox.
 ;
%

enddocument

an alternative solution is use of the adjustbox package:

documentclassarticle
usepackage[export]adjustbox
usepackagetikz
usetikzlibrarypositioning,
 shapes.multipart
usepackagemulticol
usepackageragged2e

newsaveboxtestbox

begindocument

beginlrboxtestbox
 beginminipage3inRaggedRight
 beginmulticols2
 This is a lot of bla bla bla to see what is happening. And this is more text. and a lot more. And this is more text. and a lot more. And this is more text. and a lot more.
 endmulticols
 And this is more text. and a lot more. And this is more text. and a lot more. And this is more text. and a lot more
 endminipage
endlrbox

tikz%
 node[%
 rectangle split,
 rectangle split parts=2,
 rectangle split horizontal,
 rectangle split part align=top,
 draw,
 line width=3pt
 ] (test)
 includegraphics[width=2in,valign=c]example-image-a % with "valign=c" is image baseline moved to its vertical center
 nodeparttwo useboxtestbox
 ;


enddocument

In case you could accept text box and not a TikZ node, tcolorbox offers a tcbsidebyside box where you can decide which part will adapt to its size while the other uses the available space (textwidth or box width).

documentclassarticle
usepackage[most]tcolorbox
usepackagemulticol
usepackagelmodern

begindocument
tcbsidebyside[notitle,
 sidebyside adapt=left,
 colback=white,
 enhanced,
 segmentation style=solid,
 sharp corners]
 %
 includegraphics[width=3cm]example-image-a
 %
 beginmulticols2
 This is a lot of bla bla bla to see what is happening. And this is more text. and a lot more. And this is more text. and a lot more. And this is more text. and a lot more. 
 endmulticols
 And this is more text. and a lot more. And this is more text. and a lot more. And this is more text. and a lot more
 

tcbsidebyside[notitle,
 sidebyside adapt=left,
 colback=white,
 enhanced,
 segmentation style=solid,
 sharp corners]
 %
 includegraphics[width=5cm]example-image-a
 %
 And this is more text. and a lot more. And this is more text. and a lot more. And this is more text. and a lot more
 
enddocument