Color Conversion Functions in pharos
Source:R/color-conversion-overview.R
color-conversion-overview.Rdpharos provides a family of functions for converting colors between
representations. Read each matrix as row -> column: the cell at
row X, column Y is the function that converts a color from
representation X to representation Y. - marks the diagonal
(no self-conversion), . marks a combination with no direct
function. RGB is the hub between the two tables below.
R color, hex, HSV, and RGB
| From \ To | Col | Hex | HSV | RGB |
| Col | - | colToHex() | colToHSV() | colToRGB() |
| Hex | hexToCol() | - | . | hexToRGB() |
| HSV | . | . | - | . |
| RGB | rgbToCol() | rgbToHex() | . | - |
"Col" is any valid R color specification (name, hex string, or
palette index) as accepted by grDevices::col2rgb().
No function starts from HSV: it is only ever a conversion target
(via colToHSV()), not a source – see the note below the
second table for the reason this gap is left open.
RGB, CMY, CMYK, and long integer
| From \ To | CMY | CMYK | Long | RGB |
| CMY | - | cmyToCmyk() | . | . |
| CMYK | cmykToCmy() | - | . | cmykToRgb() |
| Long | . | . | - | longToRGB() |
| RGB | rgbToCmy() | . | rgbToLong() | - |
Not part of either conversion matrix
Two related functions transform a color without changing its representation, so they don't fit a row/column slot above:
| Function | Purpose |
colToOpaque() | Computes the equivalent opaque color for a transparent color against a background – Hex stays Hex |
grayScale() | Converts colors to grayscale using luminance weighting – Col stays Col |
Why HSV has no source functions
Base R already provides the HSV -> Col/Hex direction via
grDevices::hsv(), which builds a hex color string
directly from h/s/v values – the same role rgb()
plays for RGB triplets. pharos deliberately doesn't duplicate it;
chain hsv() into colToRGB() or
colToHex() instead (see examples).
Examples
# A "." in the matrix means chaining two functions through a hub
# (usually RGB or Col), not a missing feature.
# CMY -> RGB: no direct function: CMY -> CMYK -> RGB
c(0.2, 0.6, 0.9) |> cmyToCmyk() |> cmykToRgb()
#> R G B
#> C 0.8 0.4 0.1
# Long integer -> R color name: Long -> RGB -> Col
255 |> longToRGB() |> rgbToCol()
#> [1] "red"
# HSV -> RGB: base R's hsv() bridges the gap noted above
hsv(h = 0.6, s = 0.8, v = 0.9) |> colToRGB()
#> [,1]
#> red 46
#> green 119
#> blue 230