Adding a CreateImageReader2FromExtension method

IO/Image/Testing/Python/TestTIFFReader.py

@@ -5,7 +5,7 @@ VTK_DATA_ROOT = vtkGetDataRoot()
 
 # Image pipeline
 createReader = vtk.vtkImageReader2Factory()
-reader = createReader.CreateImageReader2("" + str(VTK_DATA_ROOT) + "/Data/beach.tif")
+reader = createReader.CreateImageReader2FromExtension("tif")
 reader.SetFileName("" + str(VTK_DATA_ROOT) + "/Data/beach.tif")
 # "beach.tif" image contains ORIENTATION tag which is
 # ORIENTATION_TOPLEFT (row 0 top, col 0 lhs) type. The TIFF

IO/Image/vtkImageReader2Factory.cxx

@@ -34,6 +34,8 @@
 // until after the AvailableReaders singleton has been destroyed.
 #include "vtkFilteringInformationKeyManager.h"
 
+#include <sstream>
+
 vtkStandardNewMacro(vtkImageReader2Factory);
 
 class vtkImageReader2FactoryCleanup
@@ -112,6 +114,61 @@ vtkImageReader2* vtkImageReader2Factory::CreateImageReader2(const char* path)
   return nullptr;
 }
 
+vtkImageReader2* vtkImageReader2Factory::CreateImageReader2FromExtension(const char* extension)
+{
+  vtkImageReader2Factory::InitializeReaders();
+  vtkImageReader2* ret;
+  vtkCollection* collection = vtkCollection::New();
+  vtkObjectFactory::CreateAllInstance("vtkImageReaderObject", collection);
+  vtkObject* object;
+  // first try the current registered object factories to see
+  // if one of them can
+  for (collection->InitTraversal(); (object = collection->GetNextItemAsObject());)
+  {
+    if (object)
+    {
+      ret = vtkImageReader2::SafeDownCast(object);
+      if (ret)
+      {
+        const char* extensions = ret->GetFileExtensions();
+        if (vtkImageReader2Factory::CheckExtensionIsInExtensions(extension, extensions))
+        {
+          return ret;
+        }
+      }
+    }
+  }
+  // get rid of the collection
+  collection->Delete();
+  vtkCollectionSimpleIterator sit;
+  for (vtkImageReader2Factory::AvailableReaders->InitTraversal(sit);
+       (ret = vtkImageReader2Factory::AvailableReaders->GetNextImageReader2(sit));)
+  {
+    const char* extensions = ret->GetFileExtensions();
+    if (vtkImageReader2Factory::CheckExtensionIsInExtensions(extension, extensions))
+    {
+      return ret->NewInstance();
+    }
+  }
+  return nullptr;
+}
+
+bool vtkImageReader2Factory::CheckExtensionIsInExtensions(
+  const char* extension, const char* extensions)
+{
+
+  auto iss = std::istringstream{ extensions };
+  std::string localExtension;
+  while (iss >> localExtension)
+  {
+    if (localExtension == std::string(extension) || localExtension == "." + std::string(extension))
+    {
+      return true;
+    }
+  }
+  return false;
+}
+
 void vtkImageReader2Factory::InitializeReaders()
 {
   if (vtkImageReader2Factory::AvailableReaders)

IO/Image/vtkImageReader2Factory.h

@@ -57,18 +57,34 @@ public:
 
   /**
    * open the image file, it is the callers responsibility to call
-   * Delete on the returned object.   If no reader is found, null
+   * Delete on the returned object. If no reader is found, nullptr
    * is returned.
    */
   VTK_NEWINSTANCE
   static vtkImageReader2* CreateImageReader2(const char* path);
 
+  /**
+   * Create a vtkImageReader2 from a (dotted or not) file extension.
+   * If mulitple readers support the same extension, only one reader
+   * will be returned.
+   * It is the callers responsibility to call Delete on the returned object.
+   * If no reader is found, nullptr is returned.
+   */
+  VTK_NEWINSTANCE
+  static vtkImageReader2* CreateImageReader2FromExtension(const char* extension);
+
   /**
    * The caller must allocate the vtkImageReader2Collection and pass in the
    * pointer to this method.
    */
   static void GetRegisteredReaders(vtkImageReader2Collection*);
 
+  /*
+   * An utility method to check if a (dotted or not) file extension is present
+   * in a list a whitespace separated list of dotted file extensions
+   */
+  static bool CheckExtensionIsInExtensions(const char* extension, const char* extensions);
+
 protected:
   vtkImageReader2Factory();
   ~vtkImageReader2Factory() override;