ThresholdAdaptive: Local Adaptive Thresholding

In imagerExtra: Extra Image Processing Library Based on 'imager'

Description

Local Adaptive Thresholding

Usage

ThresholdAdaptive(im, k, windowsize = 17, range = c(0, 255))

Arguments

im	a grayscale image of class cimg
k	a numeric in the range [0,1]. when k is high, local threshold values tend to be lower. when k is low, local threshold value tend to be higher.
windowsize	windowsize controls the number of local neighborhood
range	this function assumes that the range of pixel values of of input image is [0,255] by default. you may prefer [0,1]. Note that range determines the max standard deviation. The max standard deviation plays an important role in this function.

Value

a pixel set

Author(s)

Shota Ochi

References

Faisal Shafait, Daniel Keysers, Thomas M. Breuel, "Efficient implementation of local adaptive thresholding techniques using integral images", Proc. SPIE 6815, Document Recognition and Retrieval XV, 681510 (28 January 2008)

Examples

layout(matrix(1:4, 2, 2))
plot(papers, main = "Original")
threshold(papers) %>% plot(main = "A variant of Otsu")
ThresholdAdaptive(papers, 0, range = c(0,1)) %>% plot(main = "local adaptive (k = 0)")
ThresholdAdaptive(papers, 0.2, range = c(0,1)) %>% plot(main = "local adaptive (k = 0.2)")

Example output

Loading required package: imager
Loading required package: magrittr

Attaching package: ‘imager’

The following object is masked from ‘package:magrittr’:

    add

The following objects are masked from ‘package:stats’:

    convolve, spectrum

The following object is masked from ‘package:graphics’:

    frame

The following object is masked from ‘package:base’:

    save.image

imagerExtra documentation built on May 2, 2019, 1:44 p.m.