DOC: Document Frequency Iterator(image, region) initializing at begin

Explicitly specify that those constructors from iterator types of
Modules/Filtering/ImageFrequency initialize the iterator at the begin of
the region.

Note: `FrequencyImageRegionIteratorWithIndex` and
`FrequencyImageRegionConstIteratorWithIndex` are excluded from this commit,
because they do not yet compile.

- Follow-up to pull request #4815
commit 9eb1359
"DOC: Document Iterator(image, region) constructors initializing at begin"

Author: N-Dekker

Modules/Filtering/ImageFrequency/include/itkFrequencyFFTLayoutImageRegionConstIteratorWithIndex.h

@@ -141,8 +141,8 @@ class ITK_TEMPLATE_EXPORT FrequencyFFTLayoutImageRegionConstIteratorWithIndex
     this->Init();
   }
 
-  /** Constructor establishes an iterator to walk a particular image and a
-   * particular region of that image. */
+  /** Constructor establishes an iterator to walk a particular image and a particular region of that image. Initializes
+   * the iterator at the begin of the region. */
   FrequencyFFTLayoutImageRegionConstIteratorWithIndex(const TImage * ptr, const RegionType & region)
     : ImageRegionConstIteratorWithIndex<TImage>(ptr, region)
   {

Modules/Filtering/ImageFrequency/include/itkFrequencyFFTLayoutImageRegionIteratorWithIndex.h

@@ -88,8 +88,8 @@ class FrequencyFFTLayoutImageRegionIteratorWithIndex
     : FrequencyFFTLayoutImageRegionConstIteratorWithIndex<TImage>()
   {}
 
-  /** Constructor establishes an iterator to walk a particular image and a
-   * particular region of that image. */
+  /** Constructor establishes an iterator to walk a particular image and a particular region of that image. Initializes
+   * the iterator at the begin of the region. */
   FrequencyFFTLayoutImageRegionIteratorWithIndex(TImage * ptr, const RegionType & region)
     : FrequencyFFTLayoutImageRegionConstIteratorWithIndex<TImage>(ptr, region)
   {}

Modules/Filtering/ImageFrequency/include/itkFrequencyHalfHermitianFFTLayoutImageRegionConstIteratorWithIndex.h

@@ -147,8 +147,8 @@ class FrequencyHalfHermitianFFTLayoutImageRegionConstIteratorWithIndex
     this->Init();
   }
 
-  /** Constructor establishes an iterator to walk a particular image and a
-   * particular region of that image. */
+  /** Constructor establishes an iterator to walk a particular image and a particular region of that image. Initializes
+   * the iterator at the begin of the region. */
   FrequencyHalfHermitianFFTLayoutImageRegionConstIteratorWithIndex(const TImage * ptr, const RegionType & region)
     : ImageRegionConstIteratorWithIndex<TImage>(ptr, region)
   {

Modules/Filtering/ImageFrequency/include/itkFrequencyHalfHermitianFFTLayoutImageRegionIteratorWithIndex.h

@@ -88,8 +88,8 @@ class FrequencyHalfHermitianFFTLayoutImageRegionIteratorWithIndex
     : FrequencyHalfHermitianFFTLayoutImageRegionConstIteratorWithIndex<TImage>()
   {}
 
-  /** Constructor establishes an iterator to walk a particular image and a
-   * particular region of that image. */
+  /** Constructor establishes an iterator to walk a particular image and a particular region of that image. Initializes
+   * the iterator at the begin of the region. */
   FrequencyHalfHermitianFFTLayoutImageRegionIteratorWithIndex(TImage * ptr, const RegionType & region)
     : FrequencyHalfHermitianFFTLayoutImageRegionConstIteratorWithIndex<TImage>(ptr, region)
   {}

Modules/Filtering/ImageFrequency/include/itkFrequencyShiftedFFTLayoutImageRegionConstIteratorWithIndex.h

@@ -141,8 +141,8 @@ class ITK_TEMPLATE_EXPORT FrequencyShiftedFFTLayoutImageRegionConstIteratorWithI
     this->Init();
   }
 
-  /** Constructor establishes an iterator to walk a particular image and a
-   * particular region of that image. */
+  /** Constructor establishes an iterator to walk a particular image and a particular region of that image. Initializes
+   * the iterator at the begin of the region. */
   FrequencyShiftedFFTLayoutImageRegionConstIteratorWithIndex(const TImage * ptr, const RegionType & region)
     : ImageRegionConstIteratorWithIndex<TImage>(ptr, region)
   {

Modules/Filtering/ImageFrequency/include/itkFrequencyShiftedFFTLayoutImageRegionIteratorWithIndex.h

@@ -88,8 +88,8 @@ class FrequencyShiftedFFTLayoutImageRegionIteratorWithIndex
     : FrequencyShiftedFFTLayoutImageRegionConstIteratorWithIndex<TImage>()
   {}
 
-  /** Constructor establishes an iterator to walk a particular image and a
-   * particular region of that image. */
+  /** Constructor establishes an iterator to walk a particular image and a particular region of that image. Initializes
+   * the iterator at the begin of the region. */
   FrequencyShiftedFFTLayoutImageRegionIteratorWithIndex(TImage * ptr, const RegionType & region)
     : FrequencyShiftedFFTLayoutImageRegionConstIteratorWithIndex<TImage>(ptr, region)
   {}