[vtkusers] Not able to blend properly

[Jagjeet Nain]

Hi,
it works following way:
Normal (default) : This is the standard blending mode used by OpenGL and
other graphics packages. The output always has the same number of
components and the same extent as the first input. *The alpha value of the
first input is not used in the blending computation, instead it is copied
directly to the output.*

output <- input[0]
foreach input i {
  foreach pixel px {
    r <- input[i](px)(alpha) * opacity[i]
    f <- (255 - r)
    output(px) <- output(px) * f + input(px) * r
  }
}

Cheers
On Mon, Oct 1, 2012 at 7:40 AM,  <anupriya.sharma at accenture.com> wrote:
> Hi
>
>
>
> I am trying to blend two different raw files. I have used vtkImageReader
to
> read both the files. I have applied two different lookup tables on both
the
> file
>
> I have also  used          vtkImageMapToColors ColorMapper = new
> vtkImageMapToColors();
>
>
>
>                 vtkImageMapToColors ColorMapper = new
vtkImageMapToColors();
>
>                 ColorMapper.SetInput(reader1.GetOutput());
>
>                 ColorMapper.SetLookupTable(table);
>
>
>
>                 vtkImageMapToColors ColorMapper1 = new
> vtkImageMapToColors();
>
>                 ColorMapper1.SetInput(reader2.GetOutput());
>
>                 ColorMapper1.SetLookupTable(table1);
>
>
>
> “table is the Lookuptable applied on first file and table1 is the lookup
> table applied on second file”.
>
>
>
> After setting the lookuptable I have created instance of vtkImage blend.
>
>
>
> vtkImageBlend blend = new vtkImageBlend();
>
> blend.setOpacity(0,0);
>
> blend.setOpacity(1,0);
>
> blend.AddInputConnection(ColorMapper.GetOutputPort);
>
> blend.AddInputConnection(ColorMapper1.GetOutputPort);
>
>
>
> I have later given the output of blend to the Input Connection of Viewer.
>
> Viewer.SetInputConnection(blend.GetOutputPort());
>
>
>
> But the problem is the opacity results are coming incorrect.
>
>
>
> If the opacity of first file is 0 and the opacity of second file is also 0
> then no output should be displayed but the output is getting displayed
with
> color of first LUT i.e Green.
>
> If the opacities are 0.5 and 0.5(0.5 opacity for both the files) then the
> fused color (dark green ) is getting displayed. The same color is getting
> displayed at opacities 0 and 0.5(0 for first file and 0.5 for second).The
> same thing is happening with opacities 1 and 0.5(1 for first file and 0.5
> for second).
>
>
>
> Could anyone please explain how this Opacity function is working and how
to
> blend two different files with different color tables.
>
>
>
>
>
>
>
> Regards
>
> Anupriya Sharma
>
>
>
>
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