Ported VTK cmake detection from master branch

CMakeLists.txt

@@ -140,7 +140,7 @@ OCV_OPTION(WITH_1394           "Include IEEE1394 support"                    ON
 OCV_OPTION(WITH_AVFOUNDATION   "Use AVFoundation for Video I/O"              ON   IF IOS)
 OCV_OPTION(WITH_CARBON         "Use Carbon for UI instead of Cocoa"          OFF  IF APPLE )
 OCV_OPTION(WITH_CUDA           "Include NVidia Cuda Runtime support"         ON   IF (CMAKE_VERSION VERSION_GREATER "2.8" AND NOT IOS) )
-OCV_OPTION(WITH_VTK            "Include VTK library support (and build opencv_viz module eiher)"             OFF IF (NOT ANDROID AND NOT IOS) )
+OCV_OPTION(WITH_VTK            "Include VTK library support (and build opencv_viz module eiher)"             OFF IF (NOT ANDROID AND NOT IOS AND NOT CMAKE_CROSSCOMPILING) )
 OCV_OPTION(WITH_CUFFT          "Include NVidia Cuda Fast Fourier Transform (FFT) library support"            ON  IF (CMAKE_VERSION VERSION_GREATER "2.8" AND NOT IOS) )
 OCV_OPTION(WITH_CUBLAS         "Include NVidia Cuda Basic Linear Algebra Subprograms (BLAS) library support" OFF IF (CMAKE_VERSION VERSION_GREATER "2.8" AND NOT IOS) )
 OCV_OPTION(WITH_NVCUVID        "Include NVidia Video Decoding library support"                               OFF IF (CMAKE_VERSION VERSION_GREATER "2.8" AND NOT ANDROID AND NOT IOS AND NOT APPLE) )

cmake/OpenCVDetectVTK.cmake

-if(NOT WITH_VTK OR ANDROID OR IOS)
+if(NOT WITH_VTK)
   return()
 endif()
 
 # VTK 6.x components
-find_package(VTK QUIET COMPONENTS vtkRenderingOpenGL vtkInteractionStyle vtkRenderingLOD vtkIOPLY vtkFiltersTexture vtkRenderingFreeType vtkIOExport NO_MODULE)
+find_package(VTK QUIET COMPONENTS vtkInteractionStyle vtkRenderingLOD vtkIOPLY vtkFiltersTexture vtkRenderingFreeType vtkIOExport NO_MODULE)
+IF(VTK_FOUND)
+  IF(VTK_RENDERING_BACKEND) #in vtk 7, the rendering backend is exported as a var.
+      find_package(VTK QUIET COMPONENTS vtkRendering${VTK_RENDERING_BACKEND} vtkInteractionStyle vtkRenderingLOD vtkIOPLY vtkFiltersTexture vtkRenderingFreeType vtkIOExport NO_MODULE)
+  ELSE(VTK_RENDERING_BACKEND)
+      find_package(VTK QUIET COMPONENTS vtkRenderingOpenGL vtkInteractionStyle vtkRenderingLOD vtkIOPLY vtkFiltersTexture vtkRenderingFreeType vtkIOExport NO_MODULE)
+  ENDIF(VTK_RENDERING_BACKEND)
+ENDIF(VTK_FOUND)
 
 # VTK 5.x components
 if(NOT VTK_FOUND)