<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:arial, helvetica, sans-serif;font-size:10pt"><DIV>Thank you Dan and Luis!</DIV>
<DIV>Regards </DIV>
<DIV>Juliette<BR></DIV>
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<B><SPAN style="FONT-WEIGHT: bold">De :</SPAN></B> Dan Mueller <dan.muel@gmail.com><BR><B><SPAN style="FONT-WEIGHT: bold">À :</SPAN></B> Juliette Deniau <juliette.deniau@yahoo.fr><BR><B><SPAN style="FONT-WEIGHT: bold">Cc :</SPAN></B> insight <insight-users@itk.org><BR><B><SPAN style="FONT-WEIGHT: bold">Envoyé le :</SPAN></B> Mercredi, 10 Décembre 2008, 14h48mn 10s<BR><B><SPAN style="FONT-WEIGHT: bold">Objet :</SPAN></B> Re: [Insight-users] threshold parameter in watersehd segmentation<BR></FONT><BR>Hi Juliette,<BR><BR>You may also be interested in<BR>Code/Review/itkMorphologicalWatershedFromMarkersImageFilter which does<BR>not need level/threshold values. Instead you provide a "marker" image,<BR>containing labels roughly corresponding to the desired output labels<BR>(eg. a single seed in each object of interest).<BR><BR>The Insight Journal paper can be found here:<BR> <A
href="http://www.insight-journal.org/browse/publication/92" target=_blank>http://www.insight-journal.org/browse/publication/92</A><BR><BR>Regards, Dan<BR><BR>2008/12/10 Luis Ibanez <<A href="mailto:luis.ibanez@kitware.com" ymailto="mailto:luis.ibanez@kitware.com">luis.ibanez@kitware.com</A>>:<BR>><BR>> Hi Juliette,<BR>><BR>> The Threshold parameter of the watershed filter is expected to be a<BR>> number in the range of values of the input image intensities.<BR>><BR>> This parameters will be used to define the "smallest" intensity change<BR>> in the image that will be considered as a water basin. Usually you want<BR>> to make this parameter something in the order of 1/100 or 1/1000 of the<BR>> water level (this is just a guideline, not a clear cut rule).<BR>><BR>> If you set the threshold value too low, then the filter will spend a lot<BR>> of time processing very small details of the image, that you
not<BR>> actually care about. Note that if your image has a high level of noise,<BR>> you may want to run a smoothing filter on it, before you pass it to the<BR>> watershed segmentation filter.<BR>><BR>><BR>><BR>> Regards,<BR>><BR>><BR>> Luis<BR>><BR>><BR>> --------------------<BR>> Juliette Deniau wrote:<BR>>><BR>>> Hi all,<BR>>> Could any one explain me the meaning of the threshold parameter in<BR>>> watersehdImageFilter?<BR>>> I've read the SoftwareGuide and I've understand that this parameter is<BR>>> used to generate the initial segmentation via the steepest descent stategy.<BR>>> its used to remove shallow background regions...but I couldn't understand<BR>>> its a threshold of what?<BR>>> Thank you<BR>>> Juliette<BR>>><BR>>><BR>>>
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