[vtkusers] problem displaying 2D image(the image looks darker)

[m26404030 at john.petra.ac.id]

hi all, i want to ask a question..

i want to display a 2D bitmap image (.bmp)..
i use vtkRenderWindow, vtkRenderer, vtkRenderWindowInteractor,  
vtkImageMapper, vtkActor2D, and also vtkBMPReader.
i actually can display the image but the image looks darker than the  
original image. i dont know why.
someone can tell me how to display the image correctly?