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<HTML><HEAD><TITLE>Re: [Insight-users] erosion performance for binary images</TITLE>
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<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial>Hi Dan and Gaetan,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial>First of all: thanks for your feedback.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial>I forgot about the importance of the specific choice
of the kernel. That makes sense of course. In my test code I used the
line</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial> erosionFilter->SetRadius( radii[ i ]
);</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial>and assumed it would be give a ball. Now I
use:</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial> erosionFilter->SetKernel(
itk::FlatStructuringElement<Dimension>::Box( radius )
);</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial>or</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial> erosionFilter->SetKernel(
itk::FlatStructuringElement<Dimension>::Ball( radius )
);</FONT></DIV></SPAN><SPAN class=031202716-05062009></SPAN>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial>Then the VHGW filter indeed did not run for the
Ball, because it is not decomposable.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial>The new performance results for ball and box are in the
attachments. For the box the binary erode still seems to be faster up till a
radius of 8, after which the VHGW takes over. The latter is not constant for
increasing radius though.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=031202716-05062009><FONT color=#0000ff
size=2 face=Arial>I added the source code in the zip, so you can reproduce the
results. You can also find the binary image on which I did the test in the
zip.</FONT></SPAN></DIV></DIV><BR>
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<FONT size=2 face=Tahoma><B>From:</B> Gaëtan Lehmann
[mailto:gaetan.lehmann@jouy.inra.fr] <BR></FONT></DIV></BLOCKQUOTE><PRE dir=ltr>The algorithm used in BinaryErodeImageFilter can't be easily <BR>constrained to a zone, and so it is difficult to multithread it.<BR>If you want to perform an erosion with a radius of 1 (on all the <BR>dimension), BinaryContourImageFilter followed by a SubtractImageFilter <BR>would be a lot faster (really) especially on a multicore system, as <BR>they are both multithreaded. Some timings are available in section 3 <BR>of <A href="http://insight-journal.com/download/viewpdf/217/2">http://insight-journal.com/download/viewpdf/217/2</A><BR><SPAN class=171344316-05062009> </SPAN><SPAN class=171344316-05062009> </SPAN></PRE><PRE dir=ltr><SPAN class=171344316-05062009><FONT color=#0000ff size=2 face=Arial>I just assumed it would be, since there were multi-threaded versions for grayscale images. But it's an entirely different algorithm I guess.</FONT></SPAN></PRE><PRE dir=ltr><SPAN class=171344316-05062009><FONT color=#0000ff size=2 face=Arial>Regards,</FONT></SPAN></PRE><PRE dir=ltr><SPAN class=171344316-05062009><FONT color=#0000ff size=2 face=Arial>Marius</FONT></SPAN></PRE></BODY></HTML>