11.66. ITK Sigmoid Image Filter
Remaps pixel intensities through an S-shaped (sigmoid) curve, useful for smoothly boosting contrast within a chosen intensity band.
Group (Subgroup)
ITKImageIntensity (ImageIntensity)
Description
This filter passes every pixel value through a sigmoid function — a smooth S-shaped curve. Input values near a chosen center are stretched (increasing contrast there), while values far above or below the center are gently compressed toward the output maximum or minimum. It is a common way to enhance contrast in a region of interest without the hard clipping of a threshold.
Each output pixel is computed as:
$$ \text{output} = (\text{OutputMax} - \text{OutputMin}) \cdot \frac{1}{1 + e^{-(x - \beta)/\alpha}} + \text{OutputMin} $$
where $x$ is the input pixel value.
Parameter Guidance
Alpha — the width of the transition region, in input intensity units. Larger values give a gentler, more gradual slope; smaller values give a sharper, more threshold-like transition. A negative value inverts the curve.
Beta — the center (inflection point) of the curve, in input intensity units. Input values near Beta land in the steep part of the S and are spread out the most.
Output Minimum / Output Maximum — the range the output is mapped into (defaults 0 and 255).
Required Input Sources
Operates on any scalar image — typically from Read Image, Read Images [3D Stack], or the output of a prior ITK image filter.
Input Parameter(s)
Parameter Name |
Parameter Type |
Parameter Notes |
Description |
|---|---|---|---|
Alpha |
Scalar Value |
Float64 |
The Alpha value from the Sigmoid equation. |
Beta |
Scalar Value |
Float64 |
The Beta value from the sigmoid equation |
Output Maximum |
Scalar Value |
Float64 |
The maximum output value |
Output Minimum |
Scalar Value |
Float64 |
The minimum output value |
Input Cell Data
Parameter Name |
Parameter Type |
Parameter Notes |
Description |
|---|---|---|---|
Image Geometry |
Geometry Selection |
Image |
Select the Image Geometry Group from the DataStructure. |
Input Cell Data |
Array Selection |
Allowed Types: int8, uint8, int16, uint16, int32, uint32, int64, uint64, float32, float64 |
The image data that will be processed by this filter. |
Output Cell Data
Parameter Name |
Parameter Type |
Parameter Notes |
Description |
|---|---|---|---|
Output Cell Data |
DataObjectName |
The result of the processing will be stored in this Data Array inside the same group as the input data. |
Example Pipelines
License & Copyright
Please see the description file distributed with this Plugin
DREAM3D-NX Help
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