Drop shadows

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< MetaPost | Overlays >

So you’d like to have one of these nice drop shadows behind some object? Here’s a piece of code to play with:

\startuniqueMPgraphic{mpshadow}
% BodyFontSize should be the current font size of/in the frame
mw := BodyFontSize/3;
ox := -0.5 ; % offset x
oy := -0.5 ; % offset y
bx := 1.5mw ; % bleed x (height of the shadow)
by := 1.5mw ; % bleed y (width of the shadow)
rx := 3mw ; % max. corner radius x
ry := 2mw ; % max. corner radius y
steps := 10 ; % number of shadow layers, 10 is a good value
hue := 0.015 ; % 0.02 is a good value
ycorr := 1mw ; % difference between overlay height and shadow height

for step = 1 upto steps:

	part := (step-1)/steps;
	xstep := bx * part ; % current part of bleed
	ystep := by * part ;
	crx := (rx + rx*part)/2; % current radius
	cry := (ry + ry*part)/2;

	% points of the rounded rectangle
	xa := -xstep + ox;
	xb := -xstep + ox + crx;
	xc :=  xstep + ox - crx + \overlaywidth;
	xd :=  xstep + ox       + \overlaywidth;
	ya := -ystep + ycorr + oy;
	yb := -ystep + ycorr + oy + cry;
	yc :=  ystep - ycorr + oy - cry + \overlayheight;
	yd :=  ystep - ycorr + oy       + \overlayheight;

	fill (xb, ya)---
	(xc, ya)...
	(xd, yb)---
	(xd, yc)...
	(xc, yd)---
	(xb, yd)...
	(xa, yc)---
	(xa, yb)...cycle
	withcolor transparent(1, hue, black) ;

endfor;

setbounds currentpicture to OverlayBox ;
\stopuniqueMPgraphic

\defineoverlay[shadow][\useMPgraphic{mpshadow}]

\inframed[frame=off,background=shadow,foregroundcolor=white]{\bfa This text box has a shadow.}