adding more nodes

docs/nodes/Extend Pad.md

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+# Extend Pad
+
+Add configurable borders around a DATA_FIELD using various padding methods. Useful for preparing data for FFT-based operations that suffer from edge artifacts, or for aligning fields of different sizes. Equivalent to Gwyddion's `extend.c` module.
+
+## Inputs
+
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| field | DATA_FIELD | Yes | Input field to pad |
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| padded | DATA_FIELD | Field with added borders |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| left | INT | 0 | Number of pixels to add on the left edge (0–1024) |
+| right | INT | 0 | Number of pixels to add on the right edge (0–1024) |
+| top | INT | 0 | Number of pixels to add on the top edge (0–1024) |
+| bottom | INT | 0 | Number of pixels to add on the bottom edge (0–1024) |
+| method | dropdown | mirror | Padding method: mean (fill with field mean), edge (replicate border pixels), mirror (reflect across edge), periodic (tile the field), or zero (fill with zeros) |
+
+## Notes
+
+- Mirror and periodic padding avoid sharp discontinuities at the border and are recommended before FFT-based filtering.
+- Edge padding replicates the outermost row/column of pixels into the border region.
+- Zero padding fills borders with 0.0 and can introduce step artifacts; consider mean padding as an alternative.
+- The output field's physical dimensions are extended proportionally to the added pixels.