[vtkusers] how to display RGB array/image using vtkImageImport

[Karthik Krishnan]

You need to set a lookup table on the vtkImageMapToWIndowLevelColors
(viewer->GetWindowLevel()) to get colors to show up.

  // Something like the following should do...
 imageviewer2->GetWindowLevel()->SetOutputFormatToRGB();
 vtkLookupTable *lut = vtkLookupTable::New();
 lut->SetHueRange(0.66667, 0.0);
 lut->SetSaturationRange(1, 1);
 lut->SetValueRange(1, 1);
 lut->SetAlphaRange(1, 1);
 lut->SetNumberOfColors(256);
 lut->Build();
 imageviweer2->GetWindowLevel()->SetLookupTable(lut);

-----
Or a hack to avoid settting the lookup table is...

    this->ImageViewer[0]->SetColorLevel(127.50001); // minor offset from
127.5

If you dig into the sources, you'll find out why the hack works :)


bye
--
karthik



Can you offset the level a bit and test it as:
  viewer->GetWindowLevel()->SetLevel( 127.501 );

Or else, you need to set a lookup table on the
vtkImageMapToWIndowLevelColors (viewer->GetWindowLevel()) to get colors to
show up.


On 3/5/08, Elvis Chen <elvis.chen at gmail.com> wrote:
>
> hi David,
>
> Thanks for the quick reply.  I've put the following 3 lines into my code:
>
>
>   viewer->GetWindowLevel()->SetWindow( 255.0 );
>   viewer->GetWindowLevel()->SetLevel( 127.5 );
>   viewer->GetWindowLevel()->SetLookupTable( 0 );
>
> (your 1st email was sent to me only, not to vtkusers), but I still only
> get black/white image.  Actually, the line that nulls the lookup table
> doesn't change the grabbed image at all.  Should I not use vtkImageViewer2
> at all?
>
> h.imageRGB is an int array created using "new int [ 720x480x3 ]".  What
> data scalar type should I set it to?
>
> Elvis
>
>
> On Wed, Mar 5, 2008 at 3:07 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>
> > And you might also have to set the following:
> >
> > viewer->GetWindowLevel()->SetWindow(255.0);
> > viewer->GetWindowLevel()->SetLevel(127.5);
> >
> >   David
> >
> >
> >
> > On Wed, Mar 5, 2008 at 3:04 PM, David Gobbi <david.gobbi at gmail.com>
> > wrote:
> > > Hi Elvis,
> > >
> > >  I looked at the vtkImageViewer2 code, and it creates a default color
> > >  table for you.  If you get rid of its color table, it should display
> > the RGB
> > >  data directly.
> > >
> > >  The command to get rid of the viewer's color table is as follows:
> > >
> > >  viewer->GetWindowLevel()->SetLookupTable(0);
> > >
> > >    David
> > >
> > >
> > >
> > >
> > >  On Wed, Mar 5, 2008 at 2:48 PM, Elvis Chen <elvis.chen at gmail.com>
> > wrote:
> > >  > hello,
> > >  >
> > >  > I'm trying to import video/still-images from an ultra-sound machine
> > and
> > >  > display it using vtk.  I can grab an image from the frame-grabber
> > and save
> > >  > the image as PPM (basically RGB values with some headers).  The
> > range of the
> > >  > RGB is [0..255] and I know the dimension of the image.
> > >  >
> > >  > Instead of saving it to a file I want vtk to grab the array pointer
> > and
> > >  > display it directly.  My code looks like:
> > >  >
> > >  >   vtkImageImport *importer = vtkImageImport::New();
> > >  >   importer->SetWholeExtent( 0, 719, 0, 479, 0, 0 );
> > >  >    importer->SetDataExtentToWholeExtent();
> > >  >   importer->SetDataScalarTypeToInt();
> > >  >   importer->SetNumberOfScalarComponents( 3 );
> > >  >   importer->SetImportVoidPointer( h.imageRGB );
> > >  >
> > >  >   vtkImageFlip *flip = vtkImageFlip::New();
> > >  >    flip->SetInputConnection( importer->GetOutputPort() );
> > >  >   flip->SetFilteredAxis( 1 );
> > >  >
> > >  >   vtkImageViewer2 *viewer = vtkImageViewer2::New();
> > >  >   viewer->SetInputConnection( flip->GetOutputPort() );
> > >  >    viewer->SetZSlice( 0 );
> > >  >
> > >  >
> > >  > where h.imageRGB is a pointer to integer array whose size is
> > 720x480x3.  The
> > >  > RGB are stored as [R0 G0 B0 R1 G1 B2 ... ] in h.imageRGB.  The
> > first pixel
> > >  > is on the top-left corner so I need to use vtkImageFlip to get the
> > correct
> > >  > orientation.
> > >  >
> > >  > The resulting image displayed fine except for the colour.  It looks
> > like a
> > >  > gray-scale image where as the original US image has come coloured
> > region.
> > >  > Can someone please shed some light into what might be wrong?  Is
> > there a
> > >  > function to get the range of pixel value (to 0 to 255)?
> > >  >
> > >  > Any help is very much appreciated,
> > >  >
> > >  > Elvis
> > >  >
> > >  > _______________________________________________
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> > >  >
> > >  >
> > >
> >
>
>
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