[vtkusers] differences in window/level

[José M. Rodriguez Bacallao]

hello, while I was testing a dicom viewer I am developing I noticed
differences in window leveling from the pipeline I am using with respect to
one of the viewers I use as reference. I attached the snapshot, the left
window is my viewer and the right is one of my reference viewers. Both have
the same window/level: 1995/998, but the image displayed at left is darker
than right, here is part of the pipeline I use:

        vtk_image = image.vtk_image
        self.view = vtk.QVTKWidget(self)
        self.view.setFocusProxy(self)
        # add the view to the internal layout
        self.setUpdatesEnabled(False)
        self.layout().takeAt(1)
        self.layout().addWidget(self.view)
        self.setUpdatesEnabled(True)

        # create the main interactor style
        style = vtk.vtkInteractorStyleImage()
        style.SetInteractionModeToImageSlicing()

self.view.GetRenderWindow().GetInteractor().SetInteractorStyle(style)

        # the axial orientation
        style.SetZViewRightVector((1, 0, 0))
        style.SetZViewUpVector((0, -1, 0))

        # the sagital orientation
        style.SetXViewRightVector((0, 1, 0))
        style.SetXViewUpVector((0, 0, 1))

        # the coronal orientation
        style.SetYViewRightVector((1, 0, 0))
        style.SetYViewUpVector((0, 0, 1))

        image_mapper = vtk.vtkImageResliceMapper()
        image_mapper.SliceFacesCameraOn()
        image_mapper.SliceAtFocalPointOn()
        image_mapper.JumpToNearestSliceOn()
        image_mapper.BorderOff()
        self.image_mapper = image_mapper

        format = image.image_format
        if format in (vtkgdcm.VTK_LOOKUP_TABLE,
vtkgdcm.VTK_INVERSE_LUMINANCE):
            lut = vtk_image.GetPointData().GetScalars().GetLookupTable()

            if isinstance(lut, vtkgdcm.vtkLookupTable16):
                color_filter = vtkgdcm.vtkImageMapToColors16()
            else:
                color_filter = vtk.vtkImageMapToColors()

            color_filter.SetInputConnection(vtk_image.GetProducerPort())
            color_filter.SetLookupTable(lut)

            if format == vtkgdcm.VTK_LOOKUP_TABLE:
                color_filter.SetOutputFormatToRGB()
            elif format == vtkgdcm.VTK_INVERSE_LUMINANCE:
                color_filter.SetOutputFormatToLuminance()

            color_filter.Update()
            scalar_range = color_filter.GetOutput().GetScalarRange()
            image_mapper.SetInputConnection(color_filter.GetOutputPort())
            del color_filter
        elif format == vtkgdcm.VTK_YBR:
            color_filter = vtkgdcm.vtkImageYBRToRGB()
            color_filter.SetInputConnection(vtk_image.GetProducerPort())
            color_filter.Update()
            scalar_range = color_filter.GetOutput().GetScalarRange()
            image_mapper.SetInputConnection(color_filter.GetOutputPort())
            del color_filter
        else:
            scalar_range = vtk_image.GetScalarRange()
            image_mapper.SetInput(vtk_image)

        try:
            # here the window width will be: 1995 and window level: 998
            level = image.window_level[0]
            window = image.window_width[0]
        except KeyError, IndexError:
            window = scalar_range[1] - scalar_range[0]
            level = 0.5 * (scalar_range[1] + scalar_range[0])

        image_property = vtk.vtkImageProperty()
        image_property.SetColorWindow(window)
        image_property.SetColorLevel(level)
        image_property.SetAmbient(0.0)
        image_property.SetDiffuse(1.0)
        image_property.SetOpacity(1.0)
        image_property.SetInterpolationTypeToLinear()
        self.image_property = image_property

        image_actor = vtk.vtkImageSlice()
        image_actor.SetMapper(image_mapper)
        image_actor.SetProperty(image_property)
        self.image_actor = image_actor

        image_renderer = vtk.vtkRenderer()
        image_renderer.SetBackground(0, 0, 0)
        self.image_renderer = image_renderer
        image_renderer.AddViewProp(image_actor)
        image_renderer.ResetCamera()
        image_renderer.GetActiveCamera().ParallelProjectionOn()
        self.render_window().AddRenderer(image_renderer)

        self.set_orientation('AXIAL')
        self.render()
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