STYLE: Replace loops doing Set(0) with AllocateInitialized(), in tests

Replaced `for (it.GoToBegin(); !it.IsAtEnd(); ++it)` loops doing `it.Set(0)`
with `sourceImage->AllocateInitialized()` calls.

Author: N-Dekker

Modules/Core/Common/test/itkFloodFillIteratorTest.cxx

@@ -60,18 +60,10 @@ itkFloodFillIteratorTest(int, char *[])
   // the requested region to what we just defined.
   sourceImage->SetRegions(largestPossibleRegion);
   // Now allocate memory for the sourceImage
-  sourceImage->Allocate();
+  sourceImage->AllocateInitialized();
 
   std::cout << "New sourceImage allocated" << std::endl;
 
-  // Initialize the image to hold all 0's
-  itk::ImageRegionIterator<TImageType> it(sourceImage, largestPossibleRegion);
-
-  for (it.GoToBegin(); !it.IsAtEnd(); ++it)
-  {
-    it.Set(0);
-  }
-
   //---------Create and initialize a spatial function-----------
 
   using TFunctionType = itk::SphereSpatialFunction<dim>;

Modules/Filtering/ImageGradient/test/itkDifferenceOfGaussiansGradientTest.cxx

@@ -69,18 +69,10 @@ itkDifferenceOfGaussiansGradientTest(int, char *[])
   // the requested region to what we just defined.
   sourceImage->SetRegions(largestPossibleRegion);
   // Now allocate memory for the sourceImage
-  sourceImage->Allocate();
+  sourceImage->AllocateInitialized();
 
   printf("New sourceImage allocated\n");
 
-  // Initialize the image to hold all 0's
-  itk::ImageRegionIterator<TImageType> it(sourceImage, largestPossibleRegion);
-
-  for (it.GoToBegin(); !it.IsAtEnd(); ++it)
-  {
-    it.Set(0);
-  }
-
   //---------Create and initialize a spatial function-----------
 
   using TFunctionType = itk::SphereSpatialFunction<dim>;