[ITK] Problem using Size() and iterator with ImageToListSampleAdaptor

[Paulo Guilherme Freire]

Hello.

I've been having some troubles to understand the use of Size() and iterator
when dealing with ImageToListSampleAdaptor.

Here's what I've been doing:

1) Read N images (usually N = 3) and store them in an itk::VectorImage
container.

2) Set such itk::VectorImage as input for itk::ImageToListSampleAdaptor.

3) Iterate over the list using a for loop (using the Size() method from the
ListSample) and an iterator; in both cases, count how many times the loop
was executed.

Here is my problem: when I iterate over the list using Size() I get a
different value of iterations than when I use an iterator. For example,
suppose I read three 3D (256 x 256 x 256) images. When I count the number
of iterations using an iterator (say, ListSampleType::Iterator), I get
16777216 (which is precisely 256 times 256 times 256). However, when I
count the number of iterations using a for loop (for(unsigned int = 0; i <
ListSample->Size(); ++i)), I get 50331648 (which is precisely the result of
16777216 times 3).

My question is: shouldn't the number of iterations be the same
(irregardless of whether I use an iterator or a for loop)?

The code I've been using is attached to this email. I would really
appreciate it if someone could help me solve this "mystery" :-)

Best regards,
Paulo
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CMAKE_MINIMUM_REQUIRED(VERSION 2.8)

SET( ProgramName "list_sample" )
PROJECT( ${ProgramName} )

FIND_PACKAGE (ITK REQUIRED)
IF (ITK_FOUND)
	INCLUDE( ${USE_ITK_FILE} )
ENDIF(ITK_FOUND)

INCLUDE_DIRECTORIES(
	${CMAKE_CURRENT_SOURCE_DIR} 
)

SET( SRCS
)

ADD_EXECUTABLE( ${ProgramName}
    ListSampleImages.cxx 
    ${SRCS} 
)

LINK_DIRECTORIES(
	${PROJECT_BINARY_DIR}/lib
)

TARGET_LINK_LIBRARIES( ${ProgramName}
   	${ITK_LIBRARIES}	
)
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