Calculates GLCM texture metrics of a Raster Layer

Calculates GLCM texture metrics of a RasterLayer over a sliding rectangular window

Usage

glcm_textures_wholeimage(
  r,
  n_levels,
  shift,
  metrics,
  quant_method,
  min_val,
  max_val,
  maxcell,
  na.rm,
  wopt
)

Arguments

r

A single layer SpatRaster or RasterLayer. If already quantized set quant_method to "none". The valid range of values for a quantized raster is from 0 to n_levels-1 (e.g. a raster with 32 grey levels would have a valid range of 0-31).

n_levels

Number of grey levels used in the quantization (Typically set to 16 or 32).

shift

A vector of length 2, or a list of vectors each of length 2 specifying the relationship between neighboring pixel to the reference pixel. The first number represents the shift in the x direction and the second number represents the shift in the y direction, where up and right are positive. For example c(1,0) is the pixel directly to the right. The GLCM is made symmetrical by counting each pair twice, once "forwards" and once "backwards" by interchanging reference and neighbor pixels. Therefore a shift directly to the right c(1,0) is equivalent to a shift directly to the left c(-1,0). To average over "all directions" you can use shift=list(c(1,0), c(1,1), c(0,1), c(-1,1)), which is the default.

metrics

A vector of glcm texture metrics to return. Valid entries include "glcm_contrast", "glcm_dissimilarity", "glcm_homogeneity", "glcm_ASM" (angular second moment), "glcm_entropy", "glcm_mean", "glcm_variance", "glcm_correlation".

quant_method

quantization method (either "range", "prob", or "none"). "range" quantization will create bins that cover a range of equal size. "prob" performs equal probability quantization and will use quantiles to create bins with approximately equal number of samples. "none" means the layer has already been quantized.

min_val

minimum value for equal range quantization (if not supplied, the minimum value of the raster is used)

max_val

maximum value for equal range quantization (if not supplied, the maximum value of the raster is used)

maxcell

positive integer used to take a regular sample for quantization if "prob" is used as quant_method (default is Inf)

na.rm

a logical value indicating whether NA values should be stripped before the computation proceeds (default=FALSE)

wopt

list with named options for writing files as in writeRaster

Value

a vector of texture metrics

References

Hall-Beyer, M., 2017. GLCM Texture: A Tutorial v. 3.0. University of Calgary, Alberta, Canada.

Haralick, R.M., Shanmugam, K., Dinstein, I., 1973. Textural features for image classification. IEEE Transactions on Systems, Man, and Cybernetics 610–621. https://doi.org/10.1109/TSMC.1973.4309314