Plot a three-layer pseudoRGB SpatRaster

Plot a three-layer pseudoRGB SpatRaster

Usage

hsi_plot_raster_rgb(x, stretch = NULL)

Arguments

x

A SpatRaster with hyperspectral data. Must have exactly three layers.

stretch

Character. Contrast stretch applied before rendering. One of NULL (no stretch), "lin" (linear stretch via terra::stretch()), or "hist" (histogram equalization via terra::stretch()). Default NULL.

Value

A ggplot2::ggplot object. Extend with + to add labels, themes, or colour scales.

Details

Produces a minimal RGB raster map with a fixed aspect ratio and no axis expansion. The returned ggplot carries no theme or axis labels — add these with + using standard ggplot2 conventions.

With stretch = NULL, cell values are taken as-is on a [0, 1] scale (raw reflectance). Values outside this range require stretch = "lin" or "hist", which rescale each layer to [0, 255] before rendering.

When raster unit metadata is present, the y-axis tick labels include the unit suffix such as 0 cm or 1.5 cm. If no unit metadata exists, ggplot2 default labels are used, showing pixel coordinates. Any three-band combination can be used — RGB, CIR, SWIR false colour, or any other composite.

See also

hsi_plot_raster() for single-layer plots. hsi_plot_profile() for 1-D depth profiles.

Other Plotting: hsi_plot_composite(), hsi_plot_profile(), hsi_plot_raster(), hsi_plot_spectrum()

Examples

if (FALSE) { # \dontrun{
x <- terra::rast("REFLECTANCE_testdata.tif") |> terra::subset(1:3)

# Quick pixel-space RGB plot
x_rgb <- hsi_plot_raster_rgb(x)

# With linear stretch
x_rgb <- hsi_plot_raster_rgb(x, stretch = "lin")

# Physical-space plot after calibration
um <- hsi_calibration_from_dims(scan_length_um = 50000, n_pixels = 1000)
ref <- terra::vect(cbind(1, terra::nrow(x)), type = "points")
x_physical <- hsi_set_extent(x, reference = ref, um_per_pixel = um)
x_rgb <- hsi_plot_raster_rgb(x_physical)

# Add labels and theme with ggplot2
x_rgb +
  ggplot2::labs(x = "Width (cm)", y = "Depth (cm)") +
  ggplot2::theme_minimal()
} # }