The attached image (1) shows the effect of interpolation on images; from 
left to right:

- "interpolate 0", i.e. no interpolation
- "interpolate 2", i.e. bilinear
- "interpolate 3" (currently not supported)
- "interpolate 4", i.e. normalized distance

In all cases, the black dot is exactly at the center.

As can quite easily be seen, when interpolation is activated the image 
appears slightly shifted to the bottom-right, in the order of magnitude 
of half a pixel.

Normally I'd just fix that offset, but it has probably been there since 
eons - and changing it might actually break a few scenes that have 
deliberately worked around this issue (I have at least once designed 
such a scene).

How do you feel about it?

My personal vote would be to fix it nonetheless, to end up like shown in 
the attached image (2). (And yes, that's bicubic interpolation you see 
in the "interpolate 3" field.)

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Attachments:
Download '_interpolation_shift.png' (25 KB) Download '_interpolation_fix.png' (30 KB)

Preview of image '_interpolation_shift.png'

Preview of image '_interpolation_fix.png'