[vtkusers] QVTKRenderWindowInteractor and SetSize

[Marcin Bukat]

Hello,
I have a problem resizing offscreen rendered window. The code below is
simple demo of my problem. When I run this code on linux everything work as
expected, saved 'screenshot' is of requested 320x240 resolution and UI
stays intact. On windows however SetSize() is simply ignored and screenshot
is saved in native UI resolution. Interactive resizing of vtk widget works
correctly so I guess I am missing some important bit. Any help is welcome.

PS. I use vtk6.2 and qt4.8 on both systems

#!/usr/bin/env python

import sys
import vtk
from PyQt4 import QtCore, QtGui
from vtk.qt4.QVTKRenderWindowInteractor import QVTKRenderWindowInteractor

class MainWindow(QtGui.QMainWindow):

    def __init__(self, parent = None):
        QtGui.QMainWindow.__init__(self, parent)

        self.hs = QtGui.QSplitter(QtCore.Qt.Horizontal)
        self.vs = QtGui.QSplitter(QtCore.Qt.Vertical)

        self.vspace0 = QtGui.QLabel('')
        self.vs.addWidget(self.vspace0)

        self.vtkWidget = QVTKRenderWindowInteractor(self.vs)
        self.vs.addWidget(self.vtkWidget)

        self.vspace1 = QtGui.QPushButton('Save')
        self.vs.addWidget(self.vspace1)

        self.hspace0 = QtGui.QLabel('')
        self.hs.addWidget(self.hspace0)

        self.hs.addWidget(self.vs)

        self.hspace1 = QtGui.QLabel('')
        self.hs.addWidget(self.hspace1)

        self.ren = vtk.vtkRenderer()
        self.vtkWidget.GetRenderWindow().AddRenderer(self.ren)
        self.iren = self.vtkWidget.GetRenderWindow().GetInteractor()

        # Create source
        source = vtk.vtkConeSource()
        source.SetResolution(256)

        # Create a mapper
        mapper = vtk.vtkPolyDataMapper()
        mapper.SetInputConnection(source.GetOutputPort())

        # Create an actor
        actor = vtk.vtkActor()
        actor.SetMapper(mapper)

        self.ren.AddActor(actor)

        self.ren.ResetCamera()
        self.setCentralWidget(self.hs)

        self.show()
        self.iren.SetInteractorStyle(vtk.vtkInteractorStyleRubberBandPick())
        self.iren.Initialize()

        self.vspace1.clicked.connect(self.screenshot)

    def to_image(self, renderWindow):
        windowToImageFilter = vtk.vtkWindowToImageFilter()
        windowToImageFilter.SetInput(renderWindow)
        windowToImageFilter.SetMagnification(1)
        windowToImageFilter.Update()

        return windowToImageFilter

    def screenshot(self):
        wren = self.vtkWidget.GetRenderWindow()
        w,h = wren.GetSize()
        wren.OffScreenRenderingOn()
        print((w,h))
        wren.SetSize(320,240)
        print(wren.GetSize())

        windowToImageFilter = self.to_image(wren)

        writer = vtk.vtkPNGWriter()
        writer.SetInputConnection(windowToImageFilter.GetOutputPort())
        writer.SetFileName('test_out.png')
        writer.Write()

        wren.SetSize(w,h)
        wren.OffScreenRenderingOff()

        print('Saved screenshot!')

if __name__ == "__main__":

    app = QtGui.QApplication(sys.argv)

    window = MainWindow()
    window.resize(800,800)
    window.setWindowTitle('Simple')

    sys.exit(app.exec_())
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