[vtkusers] Actors2D not magnified by vtkWindowToImageFilter->SetMagnification()

[Christopher Bruns]

  As usual vtk does just about everything I need.  And I am extremely 
grateful for the patch to correct vtkRibbonFilter that I got via this 
board a few months ago.  But I have encountered one more problem.

  I want to save an image file of my vtk render window.  I want the 
image to be of higher resolution than that shown in the vtk render 
window.  The recommended way to save such an enchanced resolution image 
is to set vtkWindowToImageFilter->SetMagnification() to a value larger 
that one.

  This methods works fine for the rendered 3D objects, but my Actor2D 
objects are either not scaled (text and polydata), or scaled but 
bizarrely placed and tiled (images).  I have included an example test 
C++ program to demonstrate the problem, in case there is anyone who has 
the time and knowledge to suggest a workaround.  Thanks in advance.

-Christopher Bruns

// Example program to demonstrate non-magnification of Actor2Ds
// TextActor and polydata are not magnified,
// while image is magnified, but is also wrongly duplicated and tiled 
across the screen

#include "vtkActor2D.h"
#include "vtkRenderer.h"
#include "vtkRenderWindow.h"
#include "vtkImageData.h"
#include "vtkTextMapper.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkInteractorStyleSwitch.h"
#include "vtkTextProperty.h"
#include "vtkWindowToImageFilter.h"
#include "vtkPNGWriter.h"
#include "vtkPoints.h"
#include "vtkCellArray.h"
#include "vtkPolyDataMapper2D.h"
#include "vtkPolyData.h"
#include "vtkProperty2D.h"
#include "vtkImageMapper.h"
#include "vtkConeSource.h"
#include "vtkActor.h"
#include "vtkPolyDataMapper.h";

int main() {
    // 3D cone
    vtkConeSource * coneSource = vtkConeSource::New();
    vtkPolyDataMapper * coneMapper = vtkPolyDataMapper::New();
    coneMapper->SetInput(coneSource->GetOutput());
    vtkActor * coneActor = vtkActor::New();
    coneActor->SetMapper(coneMapper);

    // Create small 2D image
    vtkImageData * imageData = vtkImageData::New();
    int w = 10;
    int h = 10;
    imageData->SetDimensions(w,h,1);
    imageData->SetScalarTypeToUnsignedChar();
    imageData->SetNumberOfScalarComponents(4);
    imageData->AllocateScalars();
    for (int x = 0; x < w; ++x)
        for (int y = 0; y < h; ++y) {
                imageData->SetScalarComponentFromDouble(x, y, 0, 3, 
127); // alpha
                imageData->SetScalarComponentFromDouble(x, y, 0, 0, 0); 
// red
                imageData->SetScalarComponentFromDouble(x, y, 0, 1, 
255); // green
                imageData->SetScalarComponentFromDouble(x, y, 0, 2, 0); 
// blue
        }
    vtkImageMapper * imageMapper = vtkImageMapper::New();
    imageMapper->SetInput(imageData);
    imageMapper->SetColorWindow(255.0);
    imageMapper->SetColorLevel(127.5);
    imageMapper->SetRenderToRectangle(1);
    vtkActor2D * imageActor = vtkActor2D::New();
    imageActor->SetMapper(imageMapper);
    imageActor->SetPosition(10,50);
    imageActor->SetPosition2(0.3,0.3);

    // Create Line Segment
    vtkPoints * points = vtkPoints::New();
    points->InsertNextPoint(10, 30, 0);
    points->InsertNextPoint(60, 40, 0);
   
    vtkCellArray * cells = vtkCellArray::New();
    cells->InsertNextCell(points->GetNumberOfPoints());
    for (int i = 0; i < points->GetNumberOfPoints(); i ++)
        cells->InsertCellPoint(i);

    vtkPolyData * polyData = vtkPolyData::New();
    polyData->SetPoints(points);
    polyData->SetLines(cells);
   
    vtkPolyDataMapper2D * mapper = vtkPolyDataMapper2D::New();
    mapper->SetInput(polyData);
   
    vtkActor2D * lineActor = vtkActor2D::New();
    lineActor->SetMapper(mapper);
    lineActor->GetProperty()->SetColor(1.0, 0.0, 0.0);
    lineActor->GetProperty()->SetOpacity(1.0);
    lineActor->GetProperty()->SetLineWidth(3.0);
    lineActor->SetVisibility(1);
       
    vtkTextMapper * textMapper = vtkTextMapper::New();
    textMapper->SetInput("Test String");
    textMapper->GetTextProperty()->SetColor(0, 0, 0);

    vtkActor2D * textActor = vtkActor2D::New();
    textActor->SetMapper(textMapper);
    textActor->SetPosition(10,10);

    // Renderer
    vtkRenderer *ren1 = vtkRenderer::New();
    vtkRenderWindow *renWin = vtkRenderWindow::New();
    renWin->AddRenderer(ren1);

    // Trackball interaction by default
    vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
    vtkInteractorStyleSwitch *trackBall = vtkInteractorStyleSwitch::New();
    trackBall->SetCurrentStyleToTrackballCamera();
    iren->SetInteractorStyle(trackBall);

    // Window
    iren->SetRenderWindow(renWin);
    ren1->SetBackground(1.0,1.0,1.0); // white background

    ren1->AddActor(coneActor); // magnifies perfectly
    ren1->AddActor(textActor); // no magification
    ren1->AddActor(lineActor); // no magification
    ren1->AddActor(imageActor); // magnified, but misplaced, duplicated, 
and tiled

    renWin->SetSize(100, 100);
    renWin->Render();

    // write normal sized image
    vtkWindowToImageFilter * wti = vtkWindowToImageFilter::New();
    wti->SetInput(renWin);
    wti->SetMagnification(1);
    wti->Update();

    vtkPNGWriter * pngWriter = vtkPNGWriter::New();
    pngWriter->SetFileName("normalSize.png");
    pngWriter->SetInput(wti->GetOutput());
    pngWriter->Write();

    // write magnified image
    vtkWindowToImageFilter * wti2 = vtkWindowToImageFilter::New();
    wti2->SetInput(renWin);
    wti2->SetMagnification(2);
    wti2->Update();

    vtkPNGWriter * pngWriter2 = vtkPNGWriter::New();
    pngWriter2->SetFileName("doubleSize.png");
    pngWriter2->SetInput(wti2->GetOutput());
    pngWriter2->Write();

    iren->Start();

    // Clean up data structures -- TODO - incomplete
    ren1->Delete();
    renWin->Delete();
    pngWriter->Delete();
    pngWriter2->Delete();
    wti->Delete();
    wti2->Delete();
    iren->Delete();
    trackBall->Delete();
    textActor->Delete();
    textMapper->Delete();
    lineActor->Delete();
    mapper->Delete();
    polyData->Delete();
    cells->Delete();
    points->Delete();
    imageActor->Delete();
    imageMapper->Delete();
    imageData->Delete();

    return 0;
}