Analysis: coordinate shifted results on images with ROIs and shifted origin

[PierreRaybaut]

This is a regression introduced with v0.18.0 and the associated ROI overhaul.

How to reproduce:

• Create a new 2D gaussian image with default parameters
• Shift image origin, say X₀ = Y₀ = 100
• Execute: Analysis > Centroid
• The centroid should be located at (350, 350): instead, the given result is (450, 450)