Summary:
The authors provide an image fusion framework for the Insight Toolkit. This allows for combination of multiple n-D images (although testing was restricted to 2-D and 3-D
images) for further insight.

Hypothesis:
Not applicable.

Evidence:
Input images for the examples are provided. Proper references are also given as well as identification of similar work.

Open Science:
This submission conformed to all my expectations of open science (i.e. transparent code, input/output, code explanation, etc.).

Reproducibility:
[Did you reproduce the authors’ work? yes
Did you download their code? yes
Did you compile it? yes. However, I had to make slight alterations throughout the classes. The code alterations dealt mostly with omitted 'typename' and issues involving
dynamic/const casting (mac osx, gcc 4.0, and ITK and CMake CVS).
Did you run it? yes
Did you managed to get the same results that they reported? yes
Were there information missing from the paper, that was necessary for you to reproduce the work? Other than the minor compilation difficulties, running the examples was
straightforward.

Use of Open Source Software:
Based on and extends ITK.

Open Source Contributions:
Source code was provided as was documentation on how to use the source code.

Code Quality:
The code was readable although the coding style deviates somewhat from the ITK style. This can be readily fixed by using kwsys.

Applicability to other problems:
The method was promoted as "general use" so applicability is not an issue.

Suggestions for future work:
One of the promotional details given concerns the extensibility of the image fusion toolkit. Obviously this entails that what is given is not yet complete. The author
provides an overview of what could be written but I would suggest an outline from the author as to what classes/additional features are currently being written or are
expected to be written by the author. (This is simply a request for elaboration on the comment given at the bottom of page 5.)

Perhaps related is the discussion of image fusion metrics at the bottom of page 7. Could the existing image to image metrics satisfy the requirements of image fusion
metrics?

Requests for additional information from authors:
See above.

Additional Comments:

Summary:
This paper describes an architecture for defining multiresolution wavelet decompositions of images and combining decompositions from different image sets to fuse multimodal data.


Hypothesis:
Non applicable

Evidence:
Authors provide a nice description of the motivation, the architecture, and provide a detailed example in the paper.

Open Science:
Build upon ITK. Provides filters to decompose and recompose images into wavelet coefficients at various levels. Also provides filters for operating on these pyramids.

Reproducibility:
Code built with one minor edit (#include "vnl/vnl_math.h" instead of #include "vnl_math.h").


Use of Open Source Software:
Extends upon ITK.

Open Source Contributions:
Source code provided.

Code Quality:
Template implementations should be in txx files not cxx files. There are some methods that may not be necessary. For instance, gift::MultilevelMultibandImageFilter::SetNumberOfInputImages()/OutputImages(). Not sure why these methods are needed.

The bands are represented as separate scalar images. Would another use case be for bands to be represented as components of a vector valued image? Should this be supported?

Applicability to other problems:
Wavelet decomposition and processing is a general image analysis technique. Wavelets are used not only for image processing but also as features in detection.

Suggestions for future work:


Requests for additional information from authors:

Additional Comments:
Very nice job.

Summary:
This paper presents an open-source toolkit for Image Fusion. This toolkit is based on ITK.

Hypothesis:
Non Applicable

Open Science:
This paper very much reflects the concepts of open-science and open-source.
The code is freely available and will be a great addition to the Insight Toolkit.

Reproducibility:
There was no major problem compiling the code except minor issues that should be fixed:
Compiler: MSVC 2008 Express / WinXP
In giftQmfWaveletImageFilter.h and other files I had to modiy the pow() function to avoid compilation error:

this->SetNumberOfOutputBands(pow(2.0,(int)ImageDimension));

Also I had to change:

  #include "vnl_math.h"

to

  #include "vnl/vnl_math.h"

Also, the paper specify that CMake 2.2.3 should be used, but the next release of ITK will require 2.4, so I would rather change the text to support 2.4 (which should be backward compatible anyways).

Open Source Contributions:
This paper is a great contribution to the Insight toolkit.

Code Quality:
The quality of the code is excellent, except minor style issues. The coding style is the same as ITK and should facilitate the integration into the toolkit.

Applicability to other problems:
This toolkit is very general and can be applied to many problems.

Questions for the author:
The paper refers to the scale-space image pyramid. How is this different from the current implement of MultiResolutionPyramidImageFilter?
Why not use this classe if already in the toolkit?

Suggestions for future work:
It will be great to fix the current code so that it compiles on as many platforms as possible (see previous comments).

Additional Comments:
Very good paper!