Slice display - why image in slicer is more smoothing

Hello! It is not a bug. I just wonder something about the slice display in Slicer. when I used vtk6.2 to display image with vtkImageReslice::SetInterpolationModeToLinear() and vtkImageActor:InterpolateOn(), I got Figure A which was not smoothing. But I load the same image in Slicer, then I got Figure B which was very smoothing. I tried to set output spacing of vtkImageReslice as 0.25 x original spacing, and then I got the result as slicer’s. However, I found it became slower when I paged down, and there was no this problem in slicer.

Can you tell me the additional operations has done by Slicer? Thank you very much!

Figure A
Figure B

Answer from @pieper:

Maybe the difference is that Slicer uses vtkImageReslice to resample the images to screen space (pixels on your monitor) but when you use a vtkImageActor it uses the original image as a texture.

Thank you for answering my question. Does Slicer use ImageActor to display image or use other actor?

vtkImageActor is good for simple use cases but we need many more features in 3D Slicer. Therefore, we prepare all data using VTK filter pipelines and render it by a simple actor and polydata mapper, displaying texture on a rectangle.

Thank you very much! This is very useful for me. I wil try it.