geodiv (version 1.1.0)

texture_image: Calculate Texture Metrics per Pixel

Description

Calculates the various texture metrics over windows centered on individual pixels. This creates a continuous surface of the texture metric.

Usage

texture_image(
  x,
  window_type = "square",
  size = 5,
  in_meters = FALSE,
  metric,
  args = NULL,
  parallel = TRUE,
  ncores = NULL,
  nclumps = 100
)

Value

A raster or list of rasters (if function results in multiple outputs) with pixel values representative of the metric value for the window surrounding that pixel.

Arguments

x

A raster or matrix.

window_type

Character. Type of window, either circular or square.

size

Numeric. Size of window (edge length) or diameter (in meters).

in_meters

Logical. Is the size given in meters?

metric

Character. Metric to calculate for each window. Metrics from the geodiv package are listed below.

args

List. Arguments from function to be applied over each window (e.g., list(threshold = 0.2)).

parallel

Logical. Option to run the calculations in parallel on available cores.

ncores

Numeric. If parallel is TRUE, number of cores on which to run the calculations. Defaults to all available, minus 1.

nclumps

Numeric. Number of clumps to split the raster or matrix into.

Details

Note that this function is meant to work on rasters with an equal area projection.

Metrics available from geodiv package:

1. 'sa': average surface roughness

2. 'sq': root mean square roughness

3. 's10z': ten-point height

4. 'sdq': root mean square slope of surface, 2-point method

5. 'sdq6': root mean square slope of surface, 7-point method

6. 'sdr': surface area ratio

7. 'sbi': surface bearing index

8. 'sci': core fluid retention index

9. 'ssk': skewness

10. 'sku': kurtosis

11. 'sds': summit density

12. 'sfd': 3d fractal dimension

13. 'srw': dominant radial wavelength, radial wavelength index, mean half wavelength

14. 'std': angle of dominating texture, texture direction index

15. 'svi': valley fluid retention index

16. 'stxr': texture aspect ratio

17. 'ssc': mean summit curvature

18. 'sv': maximum valley depth

19. 'sph': maximum peak height

20. 'sk': core roughness depth

21. 'smean': mean peak height

22. 'svk': reduced valley depth

23. 'spk': reduced peak height

24. 'scl': correlation length

25. 'sdc': bearing area curve height interval

Examples

# import raster image
data(normforest)
normforest <- terra::unwrap(normforest)

# crop raster to smaller area
x <- terra::crop(normforest, terra::ext(normforest[1:100, 1:100, drop = FALSE]))

# get a surface of root mean square roughness
sa_img <- texture_image(x = x, window = 'square',
size = 5, metric = 'sa',
parallel = TRUE, ncores = 1, nclumps = 20)

# plot the result
terra::plot(sa_img)