Offscreen vs. Onscreen rendering: Images are displayed with 1 voxel offset
David Gobbi?: There is an issue with Offscreen vs. Onscreen rendering of images using ResliceMapper / ImageSlice: Results seem to be shifted by one voxel, making the Offscreen result incorrect (for my work, this is a problem since I am aiming at rendering original voxels/pixels 1:1 to pixels).
There is a "minimal" example in vtkPython using VTK 8.1.2 which demonstrates the problem (attached, minimalexample.py) - the Offscreen implementation (SetOffScreenRendering(1) - i.e. screenshot_1.png) shifts the rendered image differently by 1 pixel, leaving a gap at the bottom / right side of the viewport. The Onscreen version (screenshot_0.png) is okay.
For the example, I have used vtk_logo-main1.png from the main website by additionally coloring the transparent color to white (also attached).
It can be seen that the polylines (copied from a VTK example) appear identical, so it seems that this is a problem related to displaying image data.