pliman (version 3.1.0)

mosaic_draw: Drawing Lines or Polygons with Raster Information

Description

Drawing Lines or Polygons with Raster Information

Usage

mosaic_draw(
  mosaic,
  r = 3,
  g = 2,
  b = 1,
  re = 4,
  nir = 5,
  index = "NGRDI",
  show = "rgb",
  segment = FALSE,
  viewer = c("mapview", "base"),
  threshold = "Otsu",
  invert = FALSE,
  summarize_fun = NULL,
  buffer = 2,
  color_regions = rev(grDevices::terrain.colors(50)),
  alpha = 1,
  max_pixels = 1e+06,
  downsample = NULL,
  quantiles = c(0, 1),
  plot = TRUE,
  plot_layout = c(1, 2, 3, 3)
)

Value

An invisible list containing the mosaic, draw_data, distance, distance_profile, geometry, and map.

Arguments

mosaic

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

r, g, b, re, nir

The red, green, blue, red-edge, and near-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.

index

The index to use for the index view. Defaults to "B".

show

The display option for the map view. Options are "rgb" for RGB view and "index" for index view.

segment

Should the raster object be segmented? If set to TRUE, pixels within each polygon/rectangle will be segmented based on the threshold argument.

viewer

The viewer option. If not provided, the value is retrieved using get_pliman_viewer(). This option controls the type of viewer to use for interactive plotting. The available options are "base" and "mapview". If set to "base", the base R graphics system is used for interactive plotting. If set to "mapview", the mapview package is used. To set this argument globally for all functions in the package, you can use the set_pliman_viewer() function. For example, you can run set_pliman_viewer("mapview") to set the viewer option to "mapview" for all functions.

threshold

By default (threshold = "Otsu"), a threshold value based on Otsu's method is used to reduce the grayscale image to a binary image. If a numeric value is informed, this value will be used as a threshold.

invert

Inverts the mask if desired. Defaults to FALSE.

summarize_fun

An optional function or character vector. When summarize_fun = "mean", the mean values of index are calculated within each object. For more details on available functions, refer to exactextractr::exact_extract().

buffer

Adds a buffer around the geometries of the SpatVector created. Note that the distance unit of buffer will vary according to the CRS of mosaic.

color_regions

The color palette for displaying index values. Defaults to rev(grDevices::terrain.colors(50)).

alpha

opacity of the fill color of the raster layer(s).

max_pixels

Maximum number of pixels to render in the map or plot (default: 500000).

downsample

Downsampling factor to reduce the number of pixels (default: NULL). In this case, if the number of pixels in the image (width x height) is greater than max_pixels a downsampling factor will be automatically chosen so that the number of plotted pixels approximates the max_pixels.

quantiles

the upper and lower quantiles used for color stretching.

plot

Plots the draw line/rectangle? Defaults to TRUE.

plot_layout

The de plot layout. Defaults to plot_layout = c(1, 2, 3, 3). Ie., the first row has two plots, and the second row has one plot.

Details

The mosaic_draw function enables you to create mosaic drawings from remote sensing data and compute vegetation indices.

• If a line is drawn using the "Draw Polyline" tool, the profile of index is displayed on the y-axis along the line's distance, represented in meter units. It is important to ensure that the Coordinate Reference System (CRS) of mosaic has latitude/longitude units for accurate distance representation.

• If a rectangle or polygon is drawn using the "Draw Rectangle" or "Draw Polygon" tools, the index values are calculated for each object. By default, the raw data is returned. You can set the summarize_fun to compute a summary statistic for each object.

Examples

if (interactive() && requireNamespace("EBImage")) {
library(pliman)
# Load a raster showing the elevation of Luxembourg
mosaic <- mosaic_input(system.file("ex/elev.tif", package="terra"))

# draw a polyline to see the elevation profile along the line
mosaic_draw(mosaic, buffer = 1500)
}