Median Background
Extract background using a local median filter and subtract it. The radius controls the filter window — larger values capture broader background variations. More robust than polynomial leveling for surfaces with sparse tall features. Equivalent to Gwyddion's median-bg.c module.
Inputs
| Name |
Type |
Required |
Description |
| field |
DATA_FIELD |
Yes |
Input field |
Outputs
| Name |
Type |
Description |
| result |
DATA_FIELD |
Background-subtracted field or extracted background |
Controls
| Name |
Type |
Default |
Description |
| radius |
INT |
20 |
Half-size of the median filter window in pixels; the full window is (2×radius+1)² (2–500) |
| output |
dropdown |
subtracted |
Output mode: subtracted (original minus background) or background (extracted background) |
Notes
- The median filter is robust to outliers — tall features (particles, grains) do not bias the background estimate.
- Choose a radius larger than your largest feature but smaller than the background curvature scale.
- For polynomial background removal, use Plane Level or Polynomial Level instead.
- Processing time increases with radius; for very large fields, consider downsampling first.
