[vtk-developers] 12-bit grayscale display

Uma Maheshwaran uma at lucidindia.com
Thu Feb 7 09:27:10 EST 2013


Hello David,

Thanks for the information. Please see the page 15, 16 of Totoku white
paper on GrayScale
resolution<http://www.totoku.com/display/support/pdf/Required_Grayscale_Accuracy_in_Medical_Displays(En)_V10.pdf>

I am not able to get any details about "Customized conversion table".

Please clarify following questions regarding lookup table,

   -  We are using vtkColorTransferFunction and vtkImageResliceMapper. As
   per your suggestion, we will have to change this to vtkLookupTable with
   4096 entries to support monochrome 12-bit display.

vtkSmartPointer <vtkColorTransferFunction> lookupTable = vtkSmartPointer
<vtkColorTransferFunction> :: New();
lookupTable -> AddRGBPoint(range[0], 0, 0, 0); // scalarmin
lookupTable -> AddRGBPoint(range[1], 1, 1, 1); //scalarmax

vtkSmartPointer <vtkImageProperty> imageProp = vtkSmartPointer
<vtkImageProperty> :: New();
imageProp -> SetLookupTable(lookupTable);
imageProp -> SetInterpolationTypeToNearest();

        vtkSmartPointer <vtkImageResliceMapper> mapper = vtkSmartPointer
<vtkImageResliceMapper> :: New();
mapper -> SetInputConnection(imageData -> GetProducerPort());

   - As per your suggestion in vtk-users forum, the following lookup table
   is created for 11-bit grayscale. Luminance is calculated based on the
   standard formula Y = R*0.30 + G*0.59 + B*0.11.  Please verify and I will
   try to set this 2048 entries in vtkLookuptable.

 R,G,B ->  y

 0,0,0      0

 0,0,1     0.11 (close to 0.125)

 1,0,0     0.3 (close to 0.25)

 1,0,1     0.41 (close to 0.375)

 1,0,2     0.52 (close to 0.5)

 0,1,0     0.59 (close to 0.625 )

 0,1,2     0.81 (close to 0.75)

 1,1,0     0.89 (close to 0.875)

 1,1,1     1

 1,1,2     ~1.125

 2,1,1     ~1.25

 2,1,2     ~1.375

 2,1,3     ~1.5

 1,2,1     ~1.625

 1,2,3     ~1.75

 2,2,1     ~1.875

 2,2,2     2  (....etc upto 2048 entries)


   - How to build 4096 entries lookup table?  For example, What R, G,B
   value should be used to get 0.0625 luminance?  Do we have to use alpha
   channel for generating 4096 entries?

 R,G,B,A->       y

 0,0,0 ,0          0
 0,0,0,128       ~0.0625
 0,0,1,0           ~0.125
 0,0,1,128        ~0.1875....like this etc upto 4096 entries?



Thanks,
Uma
On Wed, Feb 6, 2013 at 10:56 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> On Wed, Feb 6, 2013 at 8:58 AM, David Gobbi <david.gobbi at gmail.com> wrote:
> > On Wed, Feb 6, 2013 at 8:56 AM, David Gobbi <david.gobbi at gmail.com>
> wrote:
> >> On Wed, Feb 6, 2013 at 7:27 AM, Uma A <uma at lucidindia.com> wrote:
> >>> Hello, We are planning to use Totoku M53i2 monochrome monitor to
> visualize
> >>> industrial digital radiographic image. 12-bit display is in wishlist of
> >>> VTKImage rendering classes It is mentioned in the wishlist that
> "Likelihood:
> >>> high if someone is willing to test"- Could you please share the
> examples or
> >>> through an idea on how to test & achieve 12bit grayscale display? We
> can
> >>> possibly check and test the various cases.
> >>
> >> Page 8 of the following NVidia whitepaper describe the method that
> would be
> >> used (except that the lookup table would not be stored in a texture, it
> would
> >> be stored in a vtkLookupTable with 4096 entries.).  This method
> requires that
> >> your monitor internally converts the RGB DVI signal to a greyscale
> signal, like
> >> the monitors described in the NVidia whitepaper.
> >
> > Here is the whitepaper that I forgot to link to in my last email:
> > http://www.nvidia.ca/docs/IO/40049/Grayscale10bit_v03.pdf
>
> Follow-up: The following page on the Totoku website indicates that they use
> the same method as described in the NVidia whitepaper:
> http://www.totoku.com/display/products/feature/01.shtml
> You can easily use this method with VTK if you can get their
> "customized conversion table", because you would just have to create a
> vtkLookupTable that has the same values.
>
>  - David
>



-- 
Thanks & regards
Uma
www.kovidndt.com
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