[vtkusers] Transparent values of vtkImageData

[Alex Southern]

Hi,

Below is the code that demonstrates how I currently make vtkImageData 
that is not transparent, also attached is an image of the window showing 
this for this example code.

Right now I dont see how to modify this to make the zero values 
transparent. Any help would be greatly appreciated.

Thanks
Alex

#include <iostream>
#include <vtkSmartPointer.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkLookupTable.h>
#include <vtkFloatArray.h>
#include <vtkPointData.h>
#include <vtkImageMapToColors.h>
#include <vtkImageActor.h>
#include <vtkScalarBarActor.h>
#include <vtkImageData.h>
#include <vtkCubeSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>

using namespace std;

vtkSmartPointer<vtkLookupTable> setupLookupTable(void)
{
     vtkSmartPointer<vtkLookupTable> table = 
vtkSmartPointer<vtkLookupTable>::New();
     double r = 1.0; double g = 1.0; double b = 0.0;
     for (int x = 0; x < 64 ; x++)
     {
         if (x > 32) {    r = r + 0.0258; g = g - 0.0129; b = b - 
0.0258;    }
         if (x == 32){    r = 0.2; g = 0.4; b = 0.8;    }
         if (x < 32)    {    r = r - 0.025;    g = g - 0.0188;    b = b 
+ 0.025;    }
         table->SetTableValue(x,r,g,b,1.0);
     }
     table->SetTableValue(32,0.2,0.4,0.8,1.0); // make sure middle value 
matches background
     return table;
}

void generateArrayData( float *p, int L, int W )
{
     for (int i = 0; i < L*W; i++ ) // Generate random numbers between 
-1.0 and 1.0
     { p[i] = 2.0*(((double)(rand() / (RAND_MAX + 1.0)))-0.5); }
     for (int x = 20; x < 50; x++ ) // Add some zeros (these will be 
transparent)
     {
         for (int y = 40; y < 70; y++ )
         {
             p[x*W + y] = 0.0;
         }
     }
}

int main(int argc, char **argw)
{
     int L = 100; int W = 100; int H = 50; int len = L*W;
     float *myArray;
     myArray = new float [len];

     vtkSmartPointer<vtkCubeSource> cube = 
vtkSmartPointer<vtkCubeSource>::New();
     cube->SetXLength(L);    cube->SetYLength(W); cube->SetZLength(H);
     cube->SetCenter(L/2,W/2,-H);

     vtkSmartPointer<vtkPolyDataMapper> mapper = 
vtkSmartPointer<vtkPolyDataMapper>::New();
     mapper->SetInput(cube->GetOutput());

     vtkSmartPointer<vtkActor> cubeActor = vtkSmartPointer<vtkActor>::New();
     cubeActor->SetMapper( mapper );
     cubeActor->GetProperty()->SetColor(0.0,1.0,0.0); // make green

     vtkSmartPointer<vtkFloatArray> data = 
vtkSmartPointer<vtkFloatArray>::New();
     generateArrayData( myArray, L, W );
     data->SetArray(myArray,L*W,1);

     vtkSmartPointer<vtkImageData> imgData2DVw = 
vtkSmartPointer<vtkImageData>::New();
     imgData2DVw->SetOrigin(0,0,0);
     imgData2DVw->SetNumberOfScalarComponents(1);
     imgData2DVw->SetScalarTypeToFloat();
     imgData2DVw->SetExtent(0,L,0,W,0,0);
     imgData2DVw->SetSpacing(1.0,1.0,1.0);
     imgData2DVw->AllocateScalars();
     imgData2DVw->GetPointData()->SetScalars(data);

     vtkSmartPointer<vtkLookupTable> table = setupLookupTable();

     table->SetNumberOfTableValues(64);
     table->Build();
     table->SetScaleToLinear();
     table->SetRange(-1.0,1.0);

     vtkSmartPointer<vtkImageMapToColors> color = 
vtkSmartPointer<vtkImageMapToColors>::New();
     color->SetLookupTable(table);
     color->SetInput(imgData2DVw);

     vtkSmartPointer<vtkImageActor> imActor = 
vtkSmartPointer<vtkImageActor>::New();
     imActor->SetInput(color->GetOutput());

     vtkSmartPointer<vtkScalarBarActor> colorBar = 
vtkSmartPointer<vtkScalarBarActor>::New();
     colorBar->SetLookupTable(table);
colorBar->GetPositionCoordinate()->SetCoordinateSystemToNormalizedViewport();
     colorBar->GetPositionCoordinate()->SetValue(0.1, 0.01);
     colorBar->SetOrientationToHorizontal();
     colorBar->SetWidth(0.8);
     colorBar->SetHeight(0.12);

     vtkSmartPointer<vtkRenderer> ren1 = 
vtkSmartPointer<vtkRenderer>::New();
     vtkSmartPointer<vtkRenderWindow> renWin = 
vtkSmartPointer<vtkRenderWindow>::New();
     vtkSmartPointer<vtkRenderWindowInteractor> iren = 
vtkSmartPointer<vtkRenderWindowInteractor>::New();

     renWin->AddRenderer( ren1 );
     iren->SetRenderWindow( renWin );

     ren1->AddActor(colorBar); // Add Actors
     ren1->AddActor(imActor);
     ren1->AddActor(cubeActor);

     ren1->SetBackground(0.2, 0.4, 0.8);  // window background colour

     renWin->Render();

     iren->Start();

     delete []myArray;
   return 0;
}




On 7/10/2012 8:56 AM, Najzero wrote:
> Hi Alex,
>
> you might wanna have a look into vtkLookupTable
>
> We use it for example to have "black" values to be transparent.
>
> First build the lookuptable, then apply to the texture.
>
> <snippet we use>
> body->_volume.reset( new dicom::modDicomVolume );
>      body->_lookupTable = vtkSmartPointer<vtkLookupTable>::New();
>      body->_bmpPixelData = vtkSmartPointer<modImage>::New();   // Pixeldaten
>      body->_bmpPolyData = vtkSmartPointer<vtkPolyData>::New(); //
> Polygondaten
>      body->_texture = vtkSmartPointer<vtkTexture>::New();      // Textur
>
>      //=== set lookup table so it shows black values transparent
>      body->_lookupTable->SetNumberOfColors( 255 );
>      body->_lookupTable->SetTableRange( 0.0, 256 * 256 - 1 );
>      body->_lookupTable->SetHueRange( 0.0, 0.0 );
>      body->_lookupTable->SetSaturationRange( 0.0, 0.0 );
>      body->_lookupTable->SetAlphaRange( 0.0, 1.0 );
>      body->_lookupTable->Build();
>
>      body->_texture->SetInput( body->_bmpPixelData ); // Der Textur die
> Pixeldaten zuweisen
>      body->_texture->MapColorScalarsThroughLookupTableOn();
>      body->_texture->SetLookupTable( body->_lookupTable ); // Der Textur die
> Lookup-Table zuweisen
>
>      body->_texture->InterpolateOn();
>
>
>
> KR Adrian
>
> --
> View this message in context: http://vtk.1045678.n5.nabble.com/Transparent-values-of-vtkImageData-tp5714562p5714583.html
> Sent from the VTK - Users mailing list archive at Nabble.com.
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