Define a raster style for thumbnail rendering

stac_style() creates a normalized style object used by new_thumbnail() to render raster previews. The style describes how raster values are mapped to thumbnail pixels. It does not render the image.

Continuous styles use min/max or pmin/pmax, optionally with a color ramp supplied by palette. RGB rendering is represented by passing three band names to bands.

Categorical styles use explicit values and colors mappings. Values do not need to be sequential. Optional labels describe the categorical values and may be used to derive legends.

nodata is applied before any rendering rule and is rendered as transparent.

Usage

stac_style(
  bands = NULL,
  min = NULL,
  max = NULL,
  pmin = NULL,
  pmax = NULL,
  palette = NULL,
  values = NULL,
  colors = NULL,
  labels = NULL,
  nodata = NULL,
  opacity = NULL,
  gamma = NULL
)

Arguments

bands

Optional band name or vector of three band names. Three bands indicate RGB rendering.

min

Minimum value used for continuous stretching. Must have length one or three. Length three is only allowed when bands has length three.

max

Maximum value used for continuous stretching. Must have length one or three. Length three is only allowed when bands has length three.

pmin

Lower percentile used to derive the stretch minimum from the image. Must have length one or three. Length three is only allowed when bands has length three.

pmax

Upper percentile used to derive the stretch maximum from the image. Must have length one or three. Length three is only allowed when bands has length three.

palette

Color ramp for continuous single-band rendering. It can be a known palette name or a vector of colors.

values

Raster values for categorical rendering.

colors

Colors associated with values.

labels

Optional labels associated with values. Defaults to as.character(values).

nodata

Optional value to render as transparent. It is applied before all other rendering rules.

opacity

Optional global opacity between 0 and 1 for valid pixels.

gamma

Optional gamma correction for continuous rendering. It must not be used with categorical styles.

Value

A normalized rstatic_style object. The object also carries a mode-specific subclass: rstatic_style_categorical, rstatic_style_continuous, or rstatic_style_rgb.

Examples

# Continuous grayscale stretch
stac_style(min = 0, max = 0.5, palette = c("black", "white"))
#> <Style: continuous>
#>   stretch: min=0, max=0.5
#>   palette: black, white

# Single-band percentile stretch
stac_style(bands = "B04", pmin = 0.02, pmax = 0.98, palette = "viridis")
#> <Style: continuous>
#>   bands: B04
#>   stretch: pmin=0.02, pmax=0.98
#>   palette: viridis

# RGB composite from three bands
stac_style(bands = c("B04", "B03", "B02"), pmin = 0.02, pmax = 0.98)
#> <Style: rgb>
#>   bands: B04, B03, B02
#>   stretch: pmin=0.02, pmax=0.98

# Categorical land-cover mapping
stac_style(
  values = c(1, 2, 3),
  colors = c("#c14d00", "#367906", "#7cc900"),
  labels = c("Crop", "Forest", "Grassland"),
  nodata = 0
)
#> <Style: categorical>
#>   labels: Crop, Forest, Grassland
#>   nodata: 0