incorporate colorio

[ijlyttle]

This is also a re-imagining of the API 😬

I think that we want to focus on a "class" of color spaces that I'll call Lab-100 class. These color spaces have:

• dimensions for luminance, blue-yellow, green-red
• difference between black and white is 100
• a polar coordinate system is well founded, using chroma and hue (expressed in degrees)

Examples of these colorspaces are:

• CIELAB
• CIELUV
• CAM02-UCS
• CAM16-UCS
• JzAzBz-100 (JzAzBz, normalized to 100)

#' @param mat, `matrix` 
#' @param hex, `character` with S3 class `pth_hex`, representing a six-character hex code

To convert between different expressions of color:

#' @param color object with class `pth_hex`, `pth_mat`
# @param ... additional parameters needed to define a color space
#'  if `NULL`, will look for `color_space` attribute on `color`

pth_to_cielab <- function(color, ...) #  returns `matrix` with S3 classes `pth_mat`, `pth_cielab`
pth_to_cieluv <- function(color, ...) #  returns `matrix` with S3 classes `pth_mat`, `pth_cieluv`
pth_to_cam02ucs <- function(color, ...) #  returns `matrix` with S3 classes `pth_mat`, `pth_cam02ucs`
pth_to_cam16ucs <- function(color, ...) #  returns `matrix` with S3 classes `pth_mat`, `pth_cam16ucs`
pth_to_jzazbz100 <- function(color, ...) #  returns `matrix` with S3 classes `pth_mat`, `pth_jzazbz100`
pth_to_hex <- function(color) # returns `character` with S3 class `pth_hex`

To create a structure:

#' These functions put classes onto existing structures and values.
pth_new_cielab <- function(mat, ...) #  returns `matrix` with S3 classes `pth_mat`, `pth_cielab`
pth_new_cieluv <- function(mat, ...) #  returns `matrix` with S3 classes `pth_mat`, `pth_cieluv`
pth_new_cam02ucs <- function(mat, ...) #  returns `matrix` with S3 classes `pth_mat`, `pth_cam02ucs`
pth_new_cam16ucs <- function(mat, ...) #  returns `matrix` with S3 classes `pth_mat`, `pth_cam16ucs`
pth_new_jzazbz100 <- function(mat, ...) #  returns `matrix` with S3 classes `pth_mat`, `pth_jzazbz100`
pth_new_hex <- function(hex)  # returns `character` with S3 class `pth_hex`, representing a six-character hex code

Will also need helpers:

pth_to_cartesian <- function(mat, chroma_min = 1.e-4) # returns `matrix`
pth_to_polar <- function(mat) # returns `matrix`

Let's think a bit about the S3 classes:

pth_mat: has three columns representing luminance, blue-yellow, green-red pth_cieluv: pth_mat that uses CIELUV color space, ... pth_hex: character representing a six-character hex code