35 lines
1.9 KiB
Markdown
35 lines
1.9 KiB
Markdown
# Displacement Field
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Distort an image using synthetic displacement fields. Supports correlated Gaussian noise and tear-line distortion modes. Equivalent to Gwyddion's displfield.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 to distort |
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## Outputs
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| Name | Type | Description |
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|------|------|-------------|
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| result | DATA_FIELD | Distorted field |
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## Controls
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| Name | Type | Default | Description |
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|------|------|---------|-------------|
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| method | dropdown | gaussian_1d | Distortion method: gaussian_1d, gaussian_2d, or tear |
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| sigma | float | 5.0 | Distortion amplitude in pixels |
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| tau | float | 20.0 | Lateral correlation length in pixels |
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| density | float | 0.02 | Tear density — fraction of rows that become tear lines (tear mode only) |
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| seed | int | 42 | Random seed for reproducibility |
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## Notes
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- **gaussian_1d** generates a 1D correlated random displacement applied only in the x direction. All rows share the same displacement profile, simulating a systematic lateral distortion.
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- **gaussian_2d** generates independent 2D correlated random displacements in both x and y. This produces a more general warping of the image.
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- **tear** mode simulates scanning artifacts where random horizontal tear lines introduce sudden x-offsets that decay exponentially away from the tear row. This is useful for simulating or studying piezo slip artifacts in SPM data.
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- The **sigma** parameter controls the magnitude of the displacement. Larger values produce more extreme distortion.
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- The **tau** parameter controls the spatial correlation length. A larger tau produces smoother, more slowly varying displacement fields. The ratio sigma/tau roughly determines the local strain.
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- For realistic scanning artifacts, use tear mode with low density (0.01--0.05) and moderate sigma.
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