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ImagePro> how do dilate/erode work?

From: Jill Schmidt (jills@ocean.washington.edu)
Date: 05/25/99


Jill Schmidt <jills@ocean.washington.edu> writes:


Hi,
Can someone please tell me how these filters actually work?  For
simplicity, assume a binary image, white grains on black background.   

For dilate, does the center value of the kernel change to white if any
part of the kernel is on a white pixel?  Or does the whole kernel turn
white if any part of the kernel is on a white pixel?  Is erode the
reverse, i.e. if any part of the kernel is on a black pixel it turns the
center pixel black?  

Thanks!!  Jill


On Tue, 25 May 1999, Jill Schmidt wrote:

> Jill Schmidt <jills@ocean.washington.edu> writes:
> 
> 
> Hi Charles,
> 
> No, they aren't holes, they are "canyons", i.e., the phenomenon only
> occurs when the really bright area touches the edge of the particle.   
> Jill
> 
> ------------------------------------------------------------------------------
> 	Jill L. Schmidt			Phone:	(206) 685-1926
> 	University of Washington	FAX:	(206) 543-0275		
> 	Oceanography Box 357940		e-mail:	jills@ocean.washington.edu
> 	Seattle, WA 98195-7940
> 	 http://www.ocean.washington.edu/people/grads/jills/Schmidt.html
> ------------------------------------------------------------------------------
> 
> On Tue, 25 May 1999, Batishko, Charles R wrote:
> 
> > "Batishko, Charles R" <optiker.crb@pnl.gov> writes:
> > 
> > Jill...
> > 
> > It sounds like it may be due to the "fill holes" option (OPTIONS/FILL HOLES in
> > the COUNT/SIZE window).  Are you familiar with that?  For example, picture a
> > donut whose gray level is 150, and whose center is 255, on a background of 100.
> > Let's assume you set the high and low threshold manually to something like 125
> > to 175.  Let's also assume that you haven't checked the "fill holes" option.
> > The outer perimeter of the donut will be outlined as expected, but the bright
> > donut hole will also be outlined because it is not in the range you selected.
> > If you select the "fill holes" option, then the donut hole will be treated a
> > part of the donut, even though it is not in the range.
> > 
> > Media Cy guys...please correct me if that's not right.
> > 
> > Chuck
> > Chuck Batishko
> > PNNL - Sensors & Measurement Systems Group
> > optiker.crb@pnl.gov
> > http://www.pnl.gov/dcbpweb/batishko/batishko_cr.html
> > 
> > -----Original Message-----
> > From:	Jill Schmidt [SMTP:jills@ocean.washington.edu]
> > Sent:	Monday, May 24, 1999 11:53 AM
> > To:	imagepro-users@mediacy.com
> > Subject:	ImagePro> count/measure
> > 
> > Jill Schmidt <jills@ocean.washington.edu> writes:
> > 
> > 
> > Hi,
> > 
> > I am having a problem with counting bright particles in grey-scale images
> > (using Count). In particular, if a particle has a section in it that is
> > "too white" (around 255 on an 8 bit image), the outline of the particle
> > traces around that white section, as if the white section were equal to
> > the background (leaving big indentations in the outline). Anyone know what
> > the problem is?  Everything works great for the particles that do not
> > contain areas that are bright white.
> > 
> > Thanks, 
> > Jill
> > 
> > ------------------------------------------------------------------------------
> > 	Jill L. Schmidt			Phone:	(206) 685-1926
> > 	University of Washington	FAX:	(206) 543-0275		
> > 	Oceanography Box 357940		e-mail:	jills@ocean.washington.edu
> > 	Seattle, WA 98195-7940
> > 	 http://www.ocean.washington.edu/people/grads/jills/Schmidt.html
> > ------------------------------------------------------------------------------
> > 
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> 
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