I could do!
If someone needs done as follows.


this->SuspendLayout();


                // save old values of size
                int dimensaoNova[2], dimensaoAntiga[2];
                dimensaoAntiga[0] = plPanoramica->Size.Width;
                dimensaoAntiga[1] = plPanoramica->Size.Height;

                // to capture the values of the current monitor DPI
                float dpiX, dpiY;
                Graphics^ graphics = this->CreateGraphics();
                dpiX = graphics->DpiX;
                dpiY = graphics->DpiY;
                delete graphics;

                // the value in MM for X
                double mmX = abs(GetImageSlice()->GetXRange()[1]);

                // the value in MM to Y
                double mmY = abs(GetImageSlice()->GetYRange()[1] * GetConnectorItkVtk()->GetOutput()->GetSpacing()[1]);
                //MM * dpi / polegada
                dimensaoNova[0] = (mmX * dpiX) / 25.4;
                dimensaoNova[1] = (mmY * dpiY) / 25.4;

                // changes the renderWindow to the new value, remembering that my camera this has focused on the image using ParallelProjectionOn
                GetRenderWindow()->SetSize(dimensaoNova);

                // Convert a renderWindow to an image
                vtkSmartPointer<vtkRenderLargeImage> renderLarge = vtkSmartPointer<vtkRenderLargeImage>::New();
                renderLarge->SetInput(GetRenderer2D());
                renderLarge->SetMagnification(1);
                renderLarge->Update();
                // write the image
                vtkSmartPointer< vtkBMPWriter>jw = vtkSmartPointer<vtkBMPWriter>::New();
                jw->SetInputData(renderLarge->GetOutput());
                jw->SetFileName("d:/panoramica.bmp");
                jw->Write();

                // returns the size values for renderwindow
                GetRenderWindow()->SetSize(dimensaoAntiga);          

                this->ResumeLayout();

        
        
        
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