equalize-adapthist

equalize_adapthist

skimage.exposure.equalize_adapthist(image, *args, **kwargs) [source]

Contrast Limited Adaptive Histogram Equalization (CLAHE).

An algorithm for local contrast enhancement, that uses histograms computed over different tile regions of the image. Local details can therefore be enhanced even in regions that are darker or lighter than most of the image.

Parameters:

image : array-like Input image. kernel_size: integer or 2-tuple Defines the shape of contextual regions used in the algorithm. If an integer is given, the shape will be a square of sidelength given by this value. ntiles_x : int, optional (deprecated in favor of kernel_size) Number of tile regions in the X direction (horizontal). ntiles_y : int, optional (deprecated in favor of kernel_size) Number of tile regions in the Y direction (vertical). clip_limit : float: optional Clipping limit, normalized between 0 and 1 (higher values give more contrast). nbins : int, optional Number of gray bins for histogram (“dynamic range”).

Returns:

out : ndarray Equalized image.

See also

equalize_hist, rescale_intensity

Notes

• For color images, the following steps are performed:

  • The image is converted to HSV color space
  • The CLAHE algorithm is run on the V (Value) channel
  • The image is converted back to RGB space and returned

• For RGBA images, the original alpha channel is removed.

References

[R86]

http://tog.acm.org/resources/GraphicsGems/gems.html#gemsvi

[R87]

https://en.wikipedia.org/wiki/CLAHE#CLAHE