laplacian:MultipassFilter< { connectivity:{ default:"four"; description:"Which neighbours are compared: the 4 direct ones, or all 8 around the pixel."; label:"Neighbours"; options:{eight:"8 neighbours";four:"4 neighbours"}; type:"enum"; }; output:{ default:"signed"; description:"Signed keeps the direction of change on mid grey; Magnitude shows its size only."; label:"Output"; options:{magnitude:"Magnitude";signed:"Signed"}; type:"enum"; }; strength:{ default:1; description:"Scales the result; raise it to see faint detail."; label:"Strength"; max:10; min:0; step:0.01; type:"float"; }; }, > = ...
Second derivative of the luminance (sRGB-encoded units): the sum of the neighbours minus the
centre, with the 4-neighbour cross (centre weight −4) or the 8-neighbour ring (weights halved,
so the centre is −4 as well). Zero on flat areas and ramps; blob centres and thin lines respond
with their sign. Signed shows it on mid grey, magnitude shows |L| on black; both times
strength. Alpha is kept.
Second derivative of the luminance (sRGB-encoded units): the sum of the neighbours minus the centre, with the 4-neighbour cross (centre weight −4) or the 8-neighbour ring (weights halved, so the centre is −4 as well). Zero on flat areas and ramps; blob centres and thin lines respond with their sign. Signed shows it on mid grey, magnitude shows |L| on black; both times
strength. Alpha is kept.