Trimmed Mean
Apply a local trimmed-mean filter to a DATA_FIELD. Within each circular window, the lowest and highest fraction of pixel values are excluded before computing the mean. This provides smoothing that is more robust to outliers than a plain Gaussian or mean filter. Equivalent to Gwyddion's trimmed-mean.c module.
Inputs
| Name |
Type |
Required |
Description |
| field |
DATA_FIELD |
Yes |
Input field to filter |
Outputs
| Name |
Type |
Description |
| filtered |
DATA_FIELD |
Trimmed-mean filtered field |
Controls
| Name |
Type |
Default |
Description |
| radius |
INT |
3 |
Radius of the circular filter window in pixels (1-50) |
| trim_fraction |
FLOAT |
0.1 |
Fraction of values to exclude from each end of the sorted window (0.0-0.49) |
Notes
- A trim_fraction of 0.0 gives a plain local mean (no trimming). A trim_fraction approaching 0.5 converges to the local median.
- Typical values of 0.05-0.2 effectively suppress outlier spikes while preserving smooth features better than a median filter.
- The filter uses a circular (disc-shaped) kernel; the actual window diameter is 2*radius + 1 pixels.
- More computationally expensive than a Gaussian filter due to the sorting step within each window.
