10.137. Robust Automatic Threshold
Group (Subgroup)
Threshold
Description
This filter is automatic because it computes the threshold value itself, and robust because it derives that value from where the data changes most sharply rather than from a fixed cutoff. The user does not have to choose a threshold value manually; the filter selects one that tends to separate the input array along its sharpest boundaries. It produces a boolean Mask array that is false where the input array is less than the computed threshold and true otherwise.
The threshold is computed as a gradient-magnitude-weighted average of the input array. Each value of the input array is weighted by its corresponding gradient magnitude, so Cells that sit on strong boundaries (high gradient magnitude) contribute most to the chosen threshold, while flat interior regions (low gradient magnitude) contribute little. The result is a single threshold value T that generally partitions the input array where its gradient is highest.
The gradient magnitude measures how quickly the input field changes from one location to the next: it is large at edges or boundaries and near zero in smooth regions. It is obtained by computing the 2-norm (the square root of the sum of the squares of the per-axis derivative components) of the gradient vector at each Cell, which collapses the multi-component gradient into a single non-negative scalar value per Cell. The required gradient magnitude array can be produced with the ITK Gradient Magnitude Image Filter.
Required Input Sources
Gradient Magnitude Data – a single-component 32-bit float array giving the gradient magnitude of the input array, produced by ITK Gradient Magnitude Image Filter.
Input Parameter(s)
Parameter Name |
Parameter Type |
Parameter Notes |
Description |
|---|---|---|---|
Input Array |
Array Selection |
Allowed Types: int8, uint8, int16, uint16, int32, uint32, int64, uint64, float32, float64 Comp. Shape: 1 |
DataArray to Threshold |
Gradient Magnitude Data |
Array Selection |
Allowed Types: float32 Comp. Shape: 1 |
The complete path to the Array specifying the gradient magnitude of the Input Array |
Mask |
DataObjectName |
Created mask based on Input Array and Gradient Magnitude |
Example Pipelines
License & Copyright
Please see the description file distributed with this plugin.
DREAM3D-NX Help
If you need help, need to file a bug report or want to request a new feature, please head over to the DREAM3DNX-Issues GitHub site where the community of DREAM3D-NX users can help answer your questions.