ThresholdAdaptive {imagerExtra}

Local Adaptive Thresholding

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)")