<html><head><meta http-equiv="Content-Type" content="text/html charset=iso-8859-1"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">Hello,<div><br></div><div>You are right that the GetPixel methods are slow, but that's why iterators are recommended.</div><div><br></div><div>Currently you are trying to have you "if( featureImage2 )" in side the per-pixel loop. Not only does this cause you iterator initialization issue it also is slower of have this if statement inside the loop.</div><div><br></div><div>Here is an alternative way to construct your logic:</div><div><br></div><div><a href="https://github.com/InsightSoftwareConsortium/ITK/blob/master/Modules/Filtering/ImageFilterBase/include/itkBinaryFunctorImageFilter.hxx#L224-L297">https://github.com/InsightSoftwareConsortium/ITK/blob/master/Modules/Filtering/ImageFilterBase/include/itkBinaryFunctorImageFilter.hxx#L224-L297</a></div><div><br></div><div>Hope this help,</div><div>Brad</div><div><br><div><div>On Mar 11, 2014, at 8:34 AM, Jan Ehrhardt <<a href="mailto:ehrhardt@imi.uni-luebeck.de">ehrhardt@imi.uni-luebeck.de</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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<div text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">Hi Matt,<br>
<br>
yes, I currently use the ITK iterators, but I have the following
problem. <br>
<br>
Standard code looks like:<br>
<br>
itk::ImageRegionIterator<ImageType1> it( radius, myImage,
region );<br>
itk::ImageRegionIterator<ImageType2> featureIt1( radius,
featureImage1, region );<br>
itk::ImageRegionIterator<ImageType3> featureIt2( radius,
featureImage2, region );<br>
<br>
it.GotoBegin();<br>
featureIt1.GotoBegin();<br>
featureIt2.GotoBegin();<br>
<br>
while(!it.IsAtEnd())<br>
{<br>
// do some complicated processing stuff with or without
feature1 and/or feature2<br>
<br>
++it;<br>
++featureIt1;<br>
++featureIt2;<br>
}<br>
<br>
I only know at runtime, whether featureImage1 and/or featureImage2
are available. If<br>
featureImage1 or featureImage2 is NULL, a segmentation fault
occurs.<br>
<br>
Therefore, I have currently implemented:<br>
<br>
itk::ConstNeighborhoodIterator<ImageType1> it( radius,
myImage, region );<br>
<br>
it.GotoBegin();<br>
<br>
while(!it.IsAtEnd())<br>
{<br>
currentIndex=it.GetIndex();<br>
if( featureImage1.IsNotNull())<br>
{<br>
// use featureImage1->GetPixel(currentIndex) to process
feature 1<br>
}<br>
if( featureImage2.IsNotNull())<br>
{<br>
// use featureImage2->GetPixel(currentIndex) to process
feature 2<br>
}<br>
<br>
// do some other stuff<br>
<br>
++it;<br>
}<br>
<br>
The Image::GetPixel() method is quite time-consuming and therefore
I look for a more efficient method<br>
to implement this code (without writing four different versions).<br>
<br>
Any suggestions?<br>
<br>
Best regards,<br>
Jan<br>
<br>
On 03/11/2014 06:12 AM, Matt McCormick wrote:<br>
</div>
<blockquote cite="mid:CALzTN-RujRXRUR6UQh=3QT-bcqD8YAi8eir4bn23LBzqYLyoQA@mail.gmail.com" type="cite">
<div dir="ltr">Hi Jan,
<div><br>
</div>
<div>To iterator through an Image or VectorImage, use the
Iterators as described in the Software Guide [1]</div>
<div><br>
</div>
<div>HTH,</div>
<div>Matt</div>
<div><br>
</div>
<div>[1] <a moz-do-not-send="true" href="http://itk.org/ItkSoftwareGuide.pdf">http://itk.org/ItkSoftwareGuide.pdf</a></div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Thu, Mar 6, 2014 at 8:23 AM, Jan
Ehrhardt <span dir="ltr"><<a moz-do-not-send="true" href="mailto:ehrhardt@imi.uni-luebeck.de" target="_blank">ehrhardt@imi.uni-luebeck.de</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Hi folks,<br>
<br>
I want to iterate through a vector image without an
iterator. My approach was:<br>
<br>
MultiChannelImageType::AccessorType accessor =
pImage->GetPixelAccessor();<br>
MultiChannelImageType::InternalPixelType* pBuffer =
pImage->GetBufferPointer();<br>
<br>
for( OffsetValueType i = from; i < to; ++i )<br>
{<br>
vecPixel = accessor.Get(*pBuffer, i);<br>
}<br>
<br>
but the results are not correct (see bug(?) below). If the
bug(?) in DefaultVectorPixelAccessor is corrected (
m_OffsetMultiplier = l ) the behaviour of standard itk
iterators change. I assume, I don't understand the
parameters of DefaultVectorPixelAccessor::Get() correctly.<br>
How can I use the DefaultVectorPixelAccessor correctly?<br>
<br>
best,<br>
jan
<div class="HOEnZb">
<div class="h5"><br>
<br>
On 03/06/2014 12:25 PM, Jan Ehrhardt wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi folks,<br>
<br>
there is a bug in DefaultVectorPixelAccessor (ITK
4.4.0):<br>
<br>
void SetVectorLength(VectorLengthType l)<br>
{<br>
m_VectorLength = l;<br>
m_OffsetMultiplier = ( l - 1 );<br>
}<br>
<br>
DefaultVectorPixelAccessor(VectorLengthType l)<br>
{<br>
m_VectorLength = l;<br>
m_OffsetMultiplier = l - 1;<br>
}<br>
<br>
OffsetMultiplier should be m_OffsetMultiplier = l;<br>
<br>
Best regards,<br>
Jan<br>
<br>
</blockquote>
<br>
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