texture_image: Calculate Texture Metrics per Pixel

In geodiv: Methods for Calculating Gradient Surface Metrics

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
)

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

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.

Note

The total window size for square windows will be (size * 2) + 1.

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)

geodiv documentation built on Oct. 6, 2023, 1:07 a.m.