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Mosaic Index

Source: R/utils_mosaic.R
mosaic_index.Rd

Compute or extract an index layer from a multi-band mosaic raster.

Usage

mosaic_index(
  mosaic,
  index = "R",
  r = 3,
  g = 2,
  b = 1,
  re = NA,
  nir = NA,
  swir = NA,
  tir = NA,
  plot = TRUE,
  in_memory = TRUE,
  workers = 1
)

Arguments

mosaic

A mosaic of class SpatRaster, generally imported with mosaic_input().

index

A character value (or a vector of characters) specifying the target mode for conversion to a binary image. Use pliman_indexes_rgb() and pliman_indexes_me() to see the available RGB and multispectral indexes, respectively. Users can also calculate their own index using R, G, B, RE, NIR, SWIR, and TIR bands (eg., index = "R+B/G") or using the names of the mosaic's layers (ex., "(band_1 + band_2) / 2").

r, g, b, re, nir, swir, tir

The red, green, blue, red-edge, near-infrared, shortwave Infrared, and thermal infrared bands of the image, respectively. By default, the function assumes a BGR as input (b = 1, g = 2, r = 3). If a multispectral image is provided up to seven bands can be used to compute built-in indexes. There are no limitation of band numbers if the index is computed using the band name.

plot

Plot the computed index? Defaults to TRUE.

in_memory

Logical, indicating whether the indexes should be computed in memory. Defaults to TRUE. In most cases, this is 2-3 times faster, but errors can occur if mosaic is a large SpatRaster. If FALSE, raster algebra operations are performed on temporary files.

workers

numeric. The number of workers you want to use for parallel processing when computing multiple indexes.

Value

An index layer extracted/computed from the mosaic raster.

Details

This function computes or extracts an index layer from the input mosaic raster based on the specified index name. If the index is not found in the package's predefined index list (see image_index() for more details), it attempts to compute the index using the specified band indices. The resulting index layer is returned as an SpatRaster object.

Examples

if (interactive() && requireNamespace("EBImage")) {
library(pliman)
mosaic <- mosaic_input(system.file("ex/elev.tif", package="terra"))
names(mosaic)
elev2 <- mosaic_index(mosaic, "elevation * 5", plot = FALSE)
oldpar <- par(no.readonly=TRUE)
par(mfrow=c(1,2))

mosaic_plot(mosaic)
mosaic_plot(elev2)

# return the original parameters
par(oldpar)
}
#> Warning: The current raster is in the lat/lon coordinate system, which may result in processing errors when trying to segment individuals in the `mosaic_analyze()` function. It is highly suggested to reproject the raster using mosaic_project() with EPSG:32632
#> class       : SpatRaster 
#> dimensions  : 90, 95, 1  (nrow, ncol, nlyr)
#> resolution  : 0.008333333, 0.008333333  (x, y)
#> extent      : 5.741667, 6.533333, 49.44167, 50.19167  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 (EPSG:4326) 
#> source      : elev.tif 
#> name        : elevation 
#> min value   :       141 
#> max value   :       547 
#> Index 'elevation * 5' is not available. Trying to compute your own index.