dark tube threshold ordering

src/MATLAB/+RSF/darkTubes.m

@@ -17,11 +17,10 @@ bw = imbinarize(imn);
 bw = bwareaopen(bw,1e3);
 bw = imdilate(bw,ones(4*thickness));
 
-% imn(~bw) = 0;
-imp(~bw) = 0;
-
 imfm = fibermetric(imp);
+% NOTE as with imPreProcess, regional max first, then threshold
 imfm = imfm .* imregionalmax(imfm);
+imfm(~bw) = 0;
 
 imfm = RSF.clipRSF(imfm);