[Insight-developers] Reading vector images

[Luis Ibanez]

Jim,

The examples that were supposed to read
images of vectors were never working   :-/

They were written knowing how the reading
*should* work... that was before we realized
that there was a bug in the reading process.


   Luis


------------------------------------
Miller, James V (Research) wrote:

> Okay.
> 
> I have part of this working now. There was a minor error in the MetaIO
> object wrt to setting ComponentType verses setting PixelType for arrays.
> 
> I need to go back and check whether MetaIO writes pixel type in its header
> as META_FLOAT_ARRAY when writing vector images.  I may have editted a  
> meta header by hand to change a META_FLOAT to a META_FLOAT_ARRAY.
> 
> However, most of bug is in the ImageFileReader and ImageIOBase. My current
> solution relies on the memory layout for a Vector<T, N> being equivalent to
> the
> memory layout of an array T[N].  If we can assume this, then I have most
> of the trivial case working (I was able to read a meta image with 2D
> vectors).
> 
> One hurdle is going to be if a file has vectors of floats and the reader is
> asked to produce a vector of ints.  I'll need to modify DoConvertPixelBuffer
> to handle this.
> 
> Interesting that we have a number of examples that read vector images.  What
> file formats were these tested on?
> 
> Jim
> 
> 
> 
> -----Original Message-----
> From: Luis Ibanez [mailto:luis.ibanez at kitware.com]
> Sent: Wednesday, May 12, 2004 7:10 PM
> To: Miller, James V (Research)
> Cc: Insight-developers (E-mail); Julien Jomier
> Subject: Re: [Insight-developers] Reading vector images
> 
> 
> 
> Hi Jim,
> 
> Yes, this is a known bug in the MetaImage reader.
> 
>   http://www.itk.org/Bug/bug.php?op=show&bugid=580&pos=12
> 
> Although, as you pointed out, the error may actually
> be in the ImageFileReader<> class.
> 
> 
> If you have any hints of how to solve it,
> please go ahead   :-)
> 
> 
> Your suggestion seem to be in the right direction.
> We certainly have a lot more types defined in
> 
> 
>           ImageIOBase::SetPixelType()
> 
> that in
> 
>           ImageIOBase::GetPixelType()
> 
> 
> They should probably be made symmetrical...
> 
> 
> 
>    Luis
> 
> 
> 
> 
> ------------------------------------
> Miller, James V (Research) wrote:
> 
> 
>>I just tried to read an image of two component vectors into ITK using 
>>the Meta format.
>> 
>>I get all zeros.
>> 
>>It looks to me that in ImageFileReader::GenerateData() there is a test for
>> 
>>      m_ImageIO->GetPixelType() == typeid(TOutputImage::PixelType)
>> 
>>TOutputImage::PixelType should be Vector<float, 2>
>> 
>>m_ImageIO->GetPixelType() returns float
>> 
>>The above check for equality fails and a data conversion occurs.  The 
>>result is all zeros.
>> 
>>It looks as though people have asked this on the list before but I did 
>>not find a response.
>>I seem to recall people reading vectors as RGB pixels.
>> 
>>Perhaps if I add a GetPixelType() method to MetaImageIO that checks the 
>>m_PixelType to be VECTOR?
>> 
>> 
>> 
>>
>>*Jim Miller*
>>*/_____________________________________/*
>>/Visualization & Computer Vision//
>>/GE Research/
>>/Bldg. KW, Room C218B/
>>/P.O. Box 8, Schenectady NY 12301/
>>
>>//_millerjv at research.ge.com <mailto:millerjv at research.ge.com>_/
>>
>>/_james.miller at research.ge.com_/
>>/(518) 387-4005, Dial Comm: 8*833-4005, /
>>/Cell: (518) 505-7065, Fax: (518) 387-6981/
>>
>> 
> 
> 
> 
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