Preview a lazy object, a collected array, or a raster file.

A quick, informative plot: single band as a colour ramp with a legend, three bands as a stretched RGB composite, categorical data (few distinct values) with discrete colours. Nodata is transparent; a percentile stretch sets the colour range; axes come from the grid.

Usage

preview(
  x,
  bands = NULL,
  max_px = NULL,
  stretch = c(2, 98),
  col = grDevices::hcl.colors(64, "Viridis"),
  legend = NULL,
  main = "",
  axes = TRUE,
  xlab = "",
  ylab = "",
  na_col = NULL,
  ...
)

Arguments

x

A LazyRaster, LazyDataset, a matrix/array from collect(), or a path to a raster file.

bands

Bands to show: 1 for a colour ramp, 3 for RGB. For a LazyDataset, band names are also accepted. Defaults to the first 3 bands (RGB) or band 1.

max_px

Longest-axis pixel budget for the render; defaults to the device size.

stretch

Percentile cut c(low, high) for the colour range, or NULL for min/max.

col

Colour ramp for single-band plots.

legend

Draw a legend? Defaults to TRUE for single band, FALSE for RGB.

main, axes, xlab, ylab

Plot title, axes toggle, and axis labels.

na_col

Colour for nodata pixels, or NULL (default) to leave them transparent. Useful to make a mask's footprint explicit.

...

Unused.

Value

x, invisibly.

Details

Inputs are reduced before rendering: a file or an array is decimated to the device (or max_px); a LazyDataset/LazyRaster is re-planned at a coarse resolution so it fetches only what the preview shows (grid-pinned sources only; otherwise it collects at full resolution and decimates).

See also

draw(), which plots the pipeline rather than the data; collect() to execute at full resolution.