Distribution Coercion
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.
Inputs
| Name |
Type |
Required |
Description |
| field |
DATA_FIELD |
Yes |
Input field whose value distribution will be transformed |
Outputs
| Name |
Type |
Description |
| result |
DATA_FIELD |
Field with pixel values reassigned to match the target distribution |
Controls
| Name |
Type |
Default |
Description |
| distribution |
dropdown |
uniform |
Target distribution shape: uniform, gaussian, or levels |
| n_levels |
INT |
4 |
Number of discrete output levels (2–1000); visible only for levels mode |
| processing |
dropdown |
field |
Processing scope: field (entire array at once) or rows (line-by-line) |
Notes
- 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.
- Uniform mode spreads values evenly between the original minimum and maximum.
- Gaussian mode maps ranks to the inverse normal CDF, scaled to match the original mean and standard deviation.
- Levels mode quantizes the data into a fixed number of evenly spaced discrete values, useful for terrace-like visualization or discrete height analysis.
- Row mode applies the transformation independently to each scan line, which can correct line-to-line distribution variations in SPM data.
