[vtkusers] Show an image in true size with vtkImageViewer2

[Steven Koch]

I'm trying to use vtkImageViewer2 to generate texture maps of a 
rectilinear grid with contour lines (to project onto terrain grids). Below 
you'll see that vtkCoordinate conversion is used to 'extract' the rendered 
image from the vtkRenderWindow.  This has two problems for your 
application:  1)  the image extents change, and  2)  there will be 'pixel 
drift'.  Can anybody suggest a way to control the rendered image size? 

I will try to correct for the 'pixel drift' by using 
vtkCoordinate.GetComputedDoubleDisplayValue and correcting with the 
sub-pixel corrections when calling the final vtkImage.SetOutputOrigin and 
vtkImage.SetOutputSpacing.

        'Use vtkImageViewer2 to render images of rectilinear grid and 
contour lines to use as texture maps
        Dim m_vtkContourMapRenderer As New vtk.vtkImageViewer2
        m_vtkContourMapRenderer.SetInput(vtkBackImage)  <--- Created a 
10x10 vtkImageData with appropriate Origing and Spacing
        m_vtkContourMapRenderer.SetSliceOrientationToXY()
        m_vtkContourMapRenderer.GetRenderer.AddActor(vtkActor1)
        m_vtkContourMapRenderer.GetRenderer.AddActor(vtkActor2)
        m_vtkContourMapRenderer.GetRenderWindow.PointSmoothingOn()
        m_vtkContourMapRenderer.OffScreenRenderingOn()
        m_vtkContourMapRenderer.SetSize(1000, 1000)
 
m_vtkContourMapRenderer.GetRenderer.GetActiveCamera.ParallelProjectionOn()
        m_vtkContourMapRenderer.GetRenderer.ResetCamera()
        \
         \
          \
           \
            'Grid data range
            Dim dblRngX() As Double = 
m_vtkGrid2D.GetXCoordinates.GetRange(1)
            Dim dblRngY() As Double = 
m_vtkGrid2D.GetYCoordinates.GetRange(1)

            'Render contour map image
            m_vtkContourMapRenderer.Render()
            Dim vtkRenderedImage As New vtk.vtkWindowToImageFilter
 vtkRenderedImage.SetInput(m_vtkContourMapRenderer.GetRenderWindow)
            vtkRenderedImage.Update()

            'Extract rendered image
            Dim vtkCrnPt As New vtk.vtkCoordinate
            vtkCrnPt.SetCoordinateSystemToWorld()
            vtkCrnPt.SetValue(dblRngX(0), dblRngY(0), 0.0)
            Dim intLLPix() As Integer = 
vtkCrnPt.GetComputedDisplayValue(m_vtkContourMapRenderer.GetRenderer)
            vtkCrnPt.SetValue(dblRngX(1), dblRngY(1), 0.0)
            Dim intURPix() As Integer = 
vtkCrnPt.GetComputedDisplayValue(m_vtkContourMapRenderer.GetRenderer)
            Dim vtkExtract As New vtk.vtkImageClip
            vtkExtract.SetInputConnection(vtkRenderedImage.GetOutputPort)
            vtkExtract.ClipDataOn()
            vtkExtract.SetOutputWholeExtent(intLLPix(0), intURPix(0), 
intLLPix(1), intURPix(1), 0, 0)
            vtkExtract.Update()

            'Set the image properties
            Dim intExt() As Integer = vtkExtract.GetOutput.GetExtent
            Dim vtkImage As New vtk.vtkImageChangeInformation
            vtkImage.SetInputConnection(vtkExtract.GetOutputPort)
            vtkImage.SetOutputOrigin(dblRngX(0), dblRngY(0), 0.0)
            vtkImage.SetOutputSpacing((dblRngX(1) - dblRngX(0)) / 
(intExt(1) - intExt(0)), (dblRngY(1) - dblRngY(0)) / (intExt(3) - 
intExt(2)), 1.0)
            vtkImage.SetOutputExtentStart(0, 0, 0)
            vtkImage.Update()

Steve Koch



> Hello,
>
> I'm using vtkImageViewer2 to view my datasets and sometimes I need to 
view them in true size, so one pixel on the display corresponds always to 
one pixel on the image. How can I achieve this with the class 
vtkImageViewer2? I > know that if I use vtkImageViewer I'll get this, but 
I built a more complex 2D Viewing class with vtkImageViewer2 so I want to 
find a solution if possible with vtkImageViewer2. 
>
> Any suggestions?
>
> Thanks in advance!

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