```{index} single: Filters; ITK Adaptive Histogram Equalization Image Filter
```
# ITK Adaptive Histogram Equalization Image Filter

Power Law Adaptive Histogram Equalization.

## Group (Subgroup)

ITKImageStatistics (ImageStatistics)

## Description

Histogram equalization modifies the contrast in an image. The AdaptiveHistogramEqualizationImageFilter is a superset of many contrast enhancing filters. By modifying its parameters (alpha, beta, and window), the AdaptiveHistogramEqualizationImageFilter can produce an adaptively equalized histogram or a version of unsharp mask (local mean subtraction). Instead of applying a strict histogram equalization in a window about a pixel, this filter prescribes a mapping function (power law) controlled by the parameters alpha and beta.

The parameter alpha controls how much the filter acts like the classical histogram equalization method (alpha=0) to how much the filter acts like an unsharp mask (alpha=1).

The parameter beta controls how much the filter acts like an unsharp mask (beta=0) to much the filter acts like pass through (beta=1, with alpha=1).

The parameter window controls the size of the region over which local statistics are calculated. The size of the window is controlled by SetRadius the default Radius is 5 in all directions.

By altering alpha, beta and window, a host of equalization and unsharp masking filters is available.

The boundary condition ignores the part of the neighborhood outside the image, and over-weights the valid part of the neighborhood.

For detail description, reference "Adaptive Image Contrast Enhancement using Generalizations of Histogram Equalization." J.Alex Stark. IEEE Transactions on Image Processing, May 2000.

![](Images/ITKAdaptiveImageHistogram.png)


### Input Parameter(s)

| Parameter Name | Parameter Type | Parameter Notes | Description |
|----------------|----------------|-----------------|-------------|
| Radius | Vector of UInt32 Values | Order=X,Y,Z | Radius Dimensions XYZ |
| Alpha | Scalar Value |Float32 | Set/Get the value of alpha. Alpha = 0 produces the adaptive histogram equalization (provided beta=0). Alpha = 1 produces an unsharp mask. Default is 0.3. |
| Beta | Scalar Value |Float32 | Set/Get the value of beta. If beta = 1 (and alpha = 1), then the output image matches the input image. As beta approaches 0, the filter behaves as an unsharp mask. Default is 0.3. |

### 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

If you need help, need to file a bug report or want to request a new feature, please head over to the [DREAM3DNX-Issues](https://github.com/BlueQuartzSoftware/DREAM3DNX-Issues/discussions) GitHub site where the community of DREAM3D-NX users can help answer your questions.