Mdthbs

From page 195 of the tcolorbox manual, I can apply a "glow" effect on a circle:

documentclass{article}

usepackage[utf8]{inputenc}

usepackage{tcolorbox}

tcbuselibrary{skins}

usetikzlibrary{shadows}





begin{document}

begin{tcolorbox}[enhanced,width=2.5cm,

square,circular arc,

halign=center,valign=center,

colback=red!5!white,colframe=red!75!black,

frame style={circular glow={fill=red}} ]

tcolorbox

end{tcolorbox}





end{document}

I'm trying to set up a style with a "rectangular glow". When perusing the tikz manual, I found the following settings, which I guess are supposed to apply to a circular glow and therefore be somehow adaptable to a rectangular shape:

shadow scale=1.25, shadow xshift=0pt, shadow yshift=0pt,

fill=black, path fading={circle with fuzzy edge 15 percent},

every shadow,

Is there a way to adapt (presumably those settings) so that they work in a rectangle such as to generate a result like this one? (Just an example, not exactly the same colors.)

You might be interested in shadows.blur. There are many options how you could customize this, see texdoc pgfblur.

documentclass{article}

usepackage[utf8]{inputenc}

usepackage{tcolorbox}

tcbuselibrary{skins}

usetikzlibrary{shadows.blur}



begin{document}

begin{tcolorbox}[enhanced,width=2.5cm,

square,%circular arc,

halign=center,valign=center,

colback=red!5!white,colframe=red!75!black,

frame style={ blur shadow={shadow blur extra rounding,

shadow blur steps=10,

shadow xshift=0ex,shadow yshift=0ex,shadow blur radius=1.5ex}} 

]

tcolorbox

end{tcolorbox}

end{document}

Or

documentclass{article}

usepackage[utf8]{inputenc}

usepackage{tcolorbox}

tcbuselibrary{skins}

usetikzlibrary{shadows.blur}



begin{document}

begin{tcolorbox}[enhanced,width=2.5cm,

square,%circular arc,

halign=center,valign=center,

colback=red!5!white,colframe=red!75!black,

frame style={ blur shadow={shadow blur steps=10,shadow opacity=40,

shadow xshift=0ex,shadow yshift=0ex,shadow scale=1.05}} 

]

tcolorbox

end{tcolorbox}

end{document}

There are many options and many many ways to combine them.

The glowing effect can be achieved with Percusse's deleted answer.

documentclass{article}

usepackage[utf8]{inputenc}

usepackage{tcolorbox}

tcbuselibrary{skins}

usetikzlibrary{shadows.blur}

makeatletter

tikzset{render blur shadow/.code={pgfbs@savebb%

pgfsyssoftpath@getcurrentpath{pgfbs@input@path}%

pgfbs@compute@shadow@bbox%

pgfbs@process@rounding{pgfbs@input@path}{pgfbs@fadepath}%

pgfbs@apply@canvas@transform%

colorlet{pstb@shadow@color}{white!pgfbs@opacity!#1}%

pgfdeclarefading{shadowfading}{pgfbs@paint@fading}%

pgfsetfillcolor{#1}%

pgfsetfading{shadowfading}{pgftransformshift{pgfpoint{pgfbs@midx}{pgfbs@midy}}}%

pgfbs@usebbox{fill}%

pgfbs@restorebb%

},render blur shadow/.default=shadowcolor}

colorlet{shadowcolor}{black}

makeatother

begin{document}

pagecolor{black}

colorlet{shadowcolor}{white}

begin{tcolorbox}[enhanced,width=2.5cm,

square,halign=center,valign=center,

colback=black,colframe=black,colupper=white,

frame style={blur shadow={shadow blur steps=10,

shadow xshift=0ex,shadow yshift=0ex,shadow blur radius=1.5ex}} 

]

sffamily I am a glowing tcolorbox

end{tcolorbox}

end{document}