MarkovRandomFieldsClassifiers: Replace buffered region iteration in MRFImageFilter, remove iterator from RGBGibbsPriorFilter

[N-Dekker]

• Replaced buffered region iteration with a FillBuffer(1) call in MRFImageFilter::Allocate()
• Removed unused local region iterator labelledImageIt from RGBGibbsPriorFilter::GibbsEnergy

[greptile-apps]

Greptile Summary

This PR makes two small, clean cleanups to the MarkovRandomFieldsClassifiers module: replacing a manual buffered-region iterator loop with FillBuffer(1) in MRFImageFilter::Allocate(), and removing a dead-code iterator variable from RGBGibbsPriorFilter::GibbsEnergy.

• itkMRFImageFilter.hxx: The while (!rIter.IsAtEnd()) loop that initialized every pixel to 1 is replaced with m_LabelStatusImage->FillBuffer(1). Both operate over the buffered region and produce identical results; FillBuffer is the more idiomatic ITK approach and may use a more efficient memory fill internally. The LabelStatusImageIterator type alias in the header is retained and remains used in ApplyMRFImageFilter().
• itkRGBGibbsPriorFilter.hxx: The LabelledImageRegionIterator labelledImageIt local variable was constructed at the top of GibbsEnergy but never read or advanced — the function accesses m_LabelledImage exclusively through direct GetPixel() calls. Removing it eliminates an unnecessary iterator construction over the entire buffered region on every call to this function. The type is still legitimately used in other methods of the same file.

Confidence Score: 5/5

• This PR is safe to merge — both changes are purely mechanical, semantics-preserving cleanups with no behavioural impact.
• The FillBuffer(1) replacement is functionally identical to the loop it replaces; the removed iterator in GibbsEnergy was confirmed dead code via a full grep of usages across the module. No logic is altered, no type aliases are orphaned, and no edge cases are introduced.
• No files require special attention.

Important Files Changed

Filename	Overview
Modules/Segmentation/MarkovRandomFieldsClassifiers/include/itkMRFImageFilter.hxx	Replaces a manual while-loop iterator with FillBuffer(1) in Allocate(). The LabelStatusImageIterator type alias remains in the header and is still used in ApplyMRFImageFilter(), so no type is orphaned. The change is functionally equivalent and more idiomatic.
Modules/Segmentation/MarkovRandomFieldsClassifiers/include/itkRGBGibbsPriorFilter.hxx	Removes an unused LabelledImageRegionIterator labelledImageIt local variable from GibbsEnergy. The function accesses m_LabelledImage directly via GetPixel(), so the iterator was truly dead code. LabelledImageRegionIterator remains used in other methods.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["MRFImageFilter::Allocate()"] --> B["m_LabelStatusImage->Allocate()"]
    B --> C["m_LabelStatusImage->FillBuffer(1)\n✅ replaces manual iterator loop"]

    D["RGBGibbsPriorFilter::GibbsEnergy(i, k, k1)"] --> E["Compute offsetIndex3D from i"]
    E --> F["Access m_LabelledImage via GetPixel()"]
    F --> G["❌ labelledImageIt was constructed here\nbut never used — now removed"]
    F --> H["Return computed Gibbs energy"]

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_{Reviews (1): Last reviewed commit: "STYLE: Remove `labelledImageIt` from `RG..." | Re-trigger Greptile}