30 lines
1.3 KiB
Markdown
30 lines
1.3 KiB
Markdown
# Median Background
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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.
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## Inputs
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| Name | Type | Required | Description |
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|------|------|----------|-------------|
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| field | DATA_FIELD | Yes | Input field |
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## Outputs
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| Name | Type | Description |
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|------|------|-------------|
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| result | DATA_FIELD | Background-subtracted field or extracted background |
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## Controls
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| Name | Type | Default | Description |
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|------|------|---------|-------------|
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| radius | INT | 20 | Half-size of the median filter window in pixels; the full window is (2×radius+1)² (2-500) |
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| output | dropdown | subtracted | Output mode: subtracted (original minus background) or background (extracted background) |
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## Notes
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- The median filter is robust to outliers — tall features (particles, grains) do not bias the background estimate.
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- Choose a radius larger than your largest feature but smaller than the background curvature scale.
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- For polynomial background removal, use Plane Level or Polynomial Level instead.
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- Processing time increases with radius; for very large fields, consider downsampling first.
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