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docs/nodes/Line Correction.md

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+# Line Correction
+
+Correct scan-line mismatches using Gwyddion-derived row alignment methods. Supports median and trimmed row alignment, difference-based alignment, polynomial row leveling, and step-line correction from Gwyddion's linecorrect/linematch modules.
+
+## Inputs
+
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| field | DATA_FIELD | Yes | Input field with scan-line artifacts |
+| mask | IMAGE | No | Binary mask to include or exclude regions during correction |
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| corrected | DATA_FIELD | Field with scan-line offsets removed |
+| background | DATA_FIELD | Estimated per-line background that was subtracted |
+| row_shifts | LINE | Per-row shift values applied during correction |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| method | dropdown | median | Alignment method: median, median_diff, trimmed_mean, trimmed_diff, polynomial, or step |
+| direction | dropdown | horizontal | Direction of scan lines to correct: horizontal or vertical |
+| masking | dropdown | ignore | How to use the mask: ignore, include (correct using masked rows only), or exclude |
+| trim_fraction | FLOAT | 0.05 | Fraction of extreme values to trim; visible only for trimmed_mean and trimmed_diff methods (0–0.5) |
+| polynomial_degree | INT | 1 | Polynomial degree for the polynomial method (0–5); visible only for polynomial method |
+
+## Limitations
+
+- The step method is designed for step-like scan artifacts and may over-correct smooth surfaces.
+- Mask shape must match the field shape if a mask is connected.