[vtkusers] Fast conversion from vtkImageData to QImage?

[Prashanth Udupa]

Hi All,

I have an application where I need to convert vtkImageData to QImage. I am
using the following code for this.

Assumptions: vtkImageData is 2D. dim[0] is width, dim[1] is height. Scalars
associated with the image is always VTK_UNSIGNED_CHAR type.

QImage ConvertToQImage(vtkImageData* imageData)
{
    int dim[3];
    imageData->GetDimensions(dim);
    if(dim[0]*dim[1]*dim[2] == 0)
        return QImage();

    vtkUnsignedCharArray* scalars
        =
vtkUnsignedCharArray::SafeDownCast(imageData->GetPointData()->GetScalars());
    if(!scalars)
        return QImage();

    QImage qImage(dim[0], dim[1], QImage::Format_ARGB32);
    vtkIdType tupleIndex=0;
    unsigned char tuple[] = {0, 0, 0, 0};

    for(int j=0; j<dim[1]; j++)
    {
        for(int i=0; i<dim[0]; i++)
        {
            int r=0, g=0, b=0, a=0;
            scalars->GetTupleValue(tupleIndex++, tuple);

            switch(scalars->GetNumberOfComponents())
            {
            case 1:
                r = g = b = tuple[0];
                a = 255;
                break;
            case 2:
                r = g = b = tuple[0];
                a = tuple[1];
                break;
            case 3:
                r = tuple[0];
                g = tuple[1];
                b = tuple[2];
                a = 255;
                break;
            case 4:
                r = tuple[0];
                g = tuple[1];
                b = tuple[2];
                a = tuple[3];
                break;
            }

            QRgb color = qRgba(r, g, b, a);
            qImage.setPixel(i, j, color);
        }
    }

    return qImage;
}

I was wondering if there was a faster way to do this. If anyone has hints
for me, please do share.

Thanks very much.

Regards,
Prashanth N Udupa
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