Applies global or adaptive thresholding to a raster image, with optional masking and simple deblurring based on structural layer separation.
Usage
image_threshold(
img,
threshold = 0.4,
method = "global",
window_size = 15,
select.layer = 2,
mask.layer = 1,
binary_01 = FALSE,
deblur = FALSE
)Arguments
- img
SpatRaster object
- threshold
Numeric value (0–1). For global thresholding, it's a fraction of the global max. For adaptive thresholding, it's a fraction of local mean. For deblurring, it's the fraction of max used to recover structure.
- method
"global" or "adaptive". Ignored if `deblur = TRUE`.
- window_size
Integer (odd), only used for adaptive thresholding.
- select.layer
Integer or NULL. Which layer to use for thresholding or deblurring. If NULL and multilayer, the mean of all layers is used.
- mask.layer
Integer or NULL. If set, used to preserve masked regions or enhance structure.
- binary_01
Logical. If TRUE, binarized output uses 0/1. If FALSE, it retains max value of input.
- deblur
Logical. If TRUE, applies deblurring logic instead of standard thresholding.
Examples
img = terra::rast(seg_Oulanka2023_Session03_T067)
image_threshold(img, threshold = 0.3, method = "global")
#> class : SpatRaster
#> size : 1161, 4900, 3 (nrow, ncol, nlyr)
#> resolution : 1, 1 (x, y)
#> extent : 0, 4900, 0, 1161 (xmin, xmax, ymin, ymax)
#> coord. ref. :
#> source(s) : memory
#> names : lyr.1, lyr.2, lyr.2
#> min values : 0, 0, 0
#> max values : 255, 255, 255
image_threshold(img, threshold = 0.9, method = "adaptive", window_size = 15, binary_01 = TRUE)
#> class : SpatRaster
#> size : 1161, 4900, 3 (nrow, ncol, nlyr)
#> resolution : 1, 1 (x, y)
#> extent : 0, 4900, 0, 1161 (xmin, xmax, ymin, ymax)
#> coord. ref. :
#> source(s) : memory
#> names : lyr.1, lyr.2, lyr.2
#> min values : 0, 0, 0
#> max values : 1, 1, 1
image_threshold(img, threshold = 0.4, select.layer = 2, mask.layer = 1, deblur = TRUE)
#> class : SpatRaster
#> size : 1161, 4900, 3 (nrow, ncol, nlyr)
#> resolution : 1, 1 (x, y)
#> extent : 0, 4900, 0, 1161 (xmin, xmax, ymin, ymax)
#> coord. ref. :
#> source(s) : memory
#> names : lyr.1, lyr.2, lyr.2
#> min values : 0, 0, 0
#> max values : 255, 255, 255