Image Registration
Interactive Demonstrator · Medical Image Analysis · Uni Bern
01
Registration Explorer
02
ICP
03
Interpolation
Registration Explorer
Apply transforms to the moving image and watch similarity metrics respond in real time. Try aligning the images to maximize NCC / MI, or minimize SSD.
Fixed I
Moving T(J)
Checkerboard
|I - T(J)|
SSD (lower=better)
NCC (higher=better)
MI (higher=better)
| dashed = current
Modality
Mono-modal
Multi-modal
Transform
Rigid
Similarity
Affine
Translate X
0
Translate Y
0
Rotation
0
Scale
1.00
Scale X
1.00
Scale Y
1.00
Shear
0.00
Reset sliders
Misalign
Metrics
SSD ↓
0
NCC ↑
0
MI ↑
0
Matrix
Mono-modal
: identical contrast. SSD/NCC/MI all find the optimum.
Multi-modal
: inverted contrast (like CT vs MRI). Only
MI
finds the correct alignment — SSD has no useful minimum.
Try
Misalign
, then use sliders to re-align. Which metric guides you best?
Iterative Closest Point (ICP)
Step through ICP: find correspondences, solve Procrustes, update. Watch the cost decrease.
Target Y
Source X
Correspondences
Controls
Step
Auto-run
Reset
Initialization
Good init
Bad init
Iteration
0
Mean Error
--
Convergence
ICP
alternates nearest-neighbor matching with Procrustes.
Cost decreases monotonically but may hit a
local minimum
with poor init. Try it!
Interpolation Viewer
Rotate a pattern and compare Nearest Neighbor vs Bilinear side by side. Zoom in to see artifacts.
Nearest Neighbor
Bilinear
Controls
Rotation
15
Zoom
3x
Pattern
Checker
Cross
Brain
Nearest neighbor
: picks closest pixel. Blocky. Good for label maps.
Bilinear
: blends 4 neighbors. Smooth. Default for intensity images.
Increase rotation and zoom to see artifacts clearly.