Get Chroma and Luminance ranges for the given lightMode

Return Crange, Lrange, Cgrey, adjustRgb values for the given lightMode, intended to provide ranges suitable for contrasting text displayed on a light or dark background.

Usage

setCLranges(
  lightMode = NULL,
  Crange = getOption("jam.Crange"),
  Lrange = getOption("jam.Lrange"),
  Cgrey = getOption("jam.Cgrey", 5),
  adjustRgb = getOption("jam.adjustRgb", 0),
  setOptions = c("FALSE", "ifnull", "TRUE"),
  verbose = FALSE,
  ...
)

Arguments

lightMode

logical indicating whether the background color is light (TRUE is bright), or dark (FALSE is dark.)

When TRUE or FALSE, it will set default values for Crange and Lrange.
When NULL, it will use one or both of Crange,Lrange when supplied, and uses getOption("jam.Crange") and getOption("jam.Lrange") by default when not explicitly provided.
If lightMode is NULL and one or both of Crange, Lrange are NULL, it calls checkLightMode() then assigns appropriate default values.
To detect lightMode again, use lightMode=checkLightMode().

Crange

numeric range of chroma values, ranging between 0 and 100. By default, getOptions("Crange") is used, otherwise defaults will be assigned based upon lightMode.

Lrange

numeric range of luminance values, ranging between 0 and 100. By default, getOptions("Crange") is used, otherwise defaults will be assigned based upon lightMode.

Cgrey

numeric chroma (C) value, which defines grey colors at or below this chroma. Any colors at or below the grey cutoff will have their C values unchanged. This threshold prevents colorizing greyscale colors via Crange. To disable the effect, set Cgrey=-1.

adjustRgb

numeric color adjustment factor, used during the conversion of RGB colors to the ANSI-compatible colors used by the crayon pacakge. The ANSI color range does not include a full RGB palette, and the conversion is somewhat lossy. By default, getOptions("jam.adjustRgb") is used to store a globally re-usable value.

setOptions

character or logical whether to update options() "jam.Crange" and "jam.Lrange", with default 'FALSE'. It has the following behavior:

FALSE or "FALSE" does not update options.
TRUE or "TRUE" will update options 'jam.Crange' and 'jam.Lrange'.
"ifnull" will update only options() which were previously blank.

verbose

logical indicating whether to print verbose output.

...

additional arguments are ignored.

Value

list, invisibly, with elements:

Crange: Numeric vector of length 2, defining the HCL chroma (C) range.
Lrange: Numeric vector of length 2, defining the HCL luminance (L) range.
adjustRgb: Numeric vector of length 1, defining the adjustment to apply during RGB-to-ANSI color conversion.
Cgrey: Numeric vector of length 1, defining the HCL chroma (C) value below which colors are considered greyscale, and are converted to ANSI greyscale colors. HCL chroma ranges from 0 to 100. Set value Cgrey=-1 or Cgrey=FALSE to disable this logic, causing colors to be matched using all available ANSI color values.

Details

This function is intended mainly for internal use by jamba such as printDebug(), and make_styles(), which is also mainly intended for console text or other printed text output. The utility of this function is to store the logic of determining sensible default ranges.

Companion functions:

applyCLranges() is used to apply the ranges to a vector of R colors.
checkLightMode() is used to detect whether console output is expected to have a light or dark background.

Examples

setCLranges(lightMode=FALSE)