how to get the image postion

pingdan · August 9, 2019, 2:34am

as the graph.I show a picture in a renderer, and I know the renderer size and the picture size.when I press left button down, I can get a point position in the renderer. I want to judge if the point locate on picture. how can I get the picture position on renderer?

Edoardo_Pasca · August 9, 2019, 11:42am

You need to use vtkCoordinate

That’s how I got it working on my 3D viewer

github.com

vais-ral/CILViewer/blob/master/Wrappers/Python/ccpi/viewer/CILViewer2D.py#L742


    :return: (x,y) screen coordinate
    """


    vc = vtk.vtkCoordinate()
    vc.SetCoordinateSystemToWorld()
    vc.SetValue(world_coords)


    return vc.GetComputedDoubleDisplayValue(self.GetRenderer())




def display2imageCoordinate(self, viewerposition, subvoxel = False):
    """
    Convert display coordinates into image coordinates and add the pixel value


    :param viewerposition: (x,y) position of the selected point in the display window
    :return: (x,y,z,a) x,y,z index of the selected slice + a, the pixel value
    """
    vc = vtk.vtkCoordinate()
    vc.SetCoordinateSystemToViewport()
    vc.SetValue(viewerposition[0:2] + (0.0,))

viewerposition = interactor.GetEventPosition()
vc = vtk.vtkCoordinate()
vc.SetCoordinateSystemToViewport()
vc.SetValue(viewerposition[0:2] + (0.0,))

# pick position in World Coordinates
pickPosition = list(vc.GetComputedWorldValue(renderer))

Then I work out the location on the image by the origin and spacing. Notice that I set to 0 the third coordinate that I’m passing to vc as the viewerposition is in viewer coordinates (so 2D).

Hope this helps

Edo

pingdan · August 13, 2019, 8:12am

hi, Edo

thank you very much. I have solved my question according to your code.