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Histogram Equalization

Source: R/transform.R
histEq.Rd

histEq performs the histogram equalization of an image. The function equalizes the histogram of the input image using the following algorithm:

  • Calculate the histogram of the image.

  • Normalize the histogram so that the sum of histogram bins is 255.

  • Compute the integral of the histogram.

  • Transform the image using the integral of the histogram as a look-up table.

Usage

histEq(image, target = "new")

Arguments

image

An 8-bit (8U) Image object to transform.

target

The location where the results should be stored. It can take 3 values:

"new":

a new Image object is created and the results are stored inside (the default).

"self":

the results are stored back into image (faster but destructive).

An Image object:

the results are stored in another existing Image object. This is fast and will not replace the content of image but will replace that of target. Note that if target does not have the same dimensions, number of channels, and bit depth as image, nothing will be stored.

Value

If target="new", the function returns an Image object. If target="self", the function returns nothing and modifies image in place. If target is an Image object, the function returns nothing and modifies that Image object in place.

See also

Image, histmatch, LUT

Author

Simon Garnier, garnier@njit.edu

Examples

balloon <- image(system.file("sample_img/balloon1.png", package = "Rvision"))
balloon_eq <- histEq(balloon)