Returns the alpha (zeroth) component of fm, blurred with standard deviation σ and colorized by color. Assumes fm and color are alpha-multiplied; see Opacity (Alpha Components).
Returns a flomap that outlines fm with a radius-thick line when fm is superimposed over it. Assumes fm and color are alpha-multiplied; see Opacity (Alpha Components).
The greatest alpha value in the returned outline is the greatest alpha value in fm. Because of this, flomap-outline does fine with flomaps with fully opaque regions that are made semi-transparent:
> (define trans-text-fm (fm* 0.5 text-fm))
> (flomap->bitmap trans-text-fm)
> (flomap->bitmap (flomap-cc-superimpose (flomap-outline (flomap-inset trans-text-fm 2) 2 #(1 0 1 1)) trans-text-fm))
However, it does not do so well with flomaps that are partly opaque and partly semi-transparent: