BUG: Fix for bug 2524. Now GetBounds works when spacing is negative.

Filtering/vtkImageData.cxx

@@ -32,7 +32,7 @@
 #include "vtkVoxel.h"
 #include "vtkInformationVector.h"
 
-vtkCxxRevisionMacro(vtkImageData, "1.17");
+vtkCxxRevisionMacro(vtkImageData, "1.18");
 vtkStandardNewMacro(vtkImageData);
 
 //----------------------------------------------------------------------------
@@ -933,13 +933,18 @@ void vtkImageData::ComputeBounds()
     vtkMath::UninitializeBounds(this->Bounds);
     return;
     }
-  this->Bounds[0] = origin[0] + (extent[0] * spacing[0]);
-  this->Bounds[2] = origin[1] + (extent[2] * spacing[1]);
-  this->Bounds[4] = origin[2] + (extent[4] * spacing[2]);
 
-  this->Bounds[1] = origin[0] + (extent[1] * spacing[0]);
-  this->Bounds[3] = origin[1] + (extent[3] * spacing[1]);
-  this->Bounds[5] = origin[2] + (extent[5] * spacing[2]);
+  int swapXBounds = (spacing[0] < 0);  // 1 if true, 0 if false
+  int swapYBounds = (spacing[1] < 0);  // 1 if true, 0 if false
+  int swapZBounds = (spacing[2] < 0);  // 1 if true, 0 if false
+    
+  this->Bounds[0] = origin[0] + (extent[0+swapXBounds] * spacing[0]);
+  this->Bounds[2] = origin[1] + (extent[2+swapYBounds] * spacing[1]);
+  this->Bounds[4] = origin[2] + (extent[4+swapZBounds] * spacing[2]);
+
+  this->Bounds[1] = origin[0] + (extent[1-swapXBounds] * spacing[0]);
+  this->Bounds[3] = origin[1] + (extent[3-swapYBounds] * spacing[1]);
+  this->Bounds[5] = origin[2] + (extent[5-swapZBounds] * spacing[2]);
 }
 
 //----------------------------------------------------------------------------