32 lines
1.6 KiB
Markdown
32 lines
1.6 KiB
Markdown
# Distribution Coercion
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Transform pixel values so their distribution matches a target shape (uniform, Gaussian, or discrete levels) using rank-based reassignment. Equivalent to Gwyddion's coerce.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 whose value distribution will be transformed |
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## Outputs
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| Name | Type | Description |
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|------|------|-------------|
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| result | DATA_FIELD | Field with pixel values reassigned to match the target distribution |
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## Controls
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| Name | Type | Default | Description |
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|------|------|---------|-------------|
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| distribution | dropdown | uniform | Target distribution shape: uniform, gaussian, or levels |
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| n_levels | INT | 4 | Number of discrete output levels (2–1000); visible only for levels mode |
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| processing | dropdown | field | Processing scope: field (entire array at once) or rows (line-by-line) |
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## Notes
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- The transformation is rank-based: pixels are sorted, then reassigned values drawn from the target distribution in sorted order. This preserves the relative ordering of all pixel values.
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- Uniform mode spreads values evenly between the original minimum and maximum.
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- Gaussian mode maps ranks to the inverse normal CDF, scaled to match the original mean and standard deviation.
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- Levels mode quantizes the data into a fixed number of evenly spaced discrete values, useful for terrace-like visualization or discrete height analysis.
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- Row mode applies the transformation independently to each scan line, which can correct line-to-line distribution variations in SPM data.
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