postcss-color-hwb/index.js

/**
 * Module dependencies.
 */
var postcss = require("postcss")
var helpers = require("postcss-message-helpers")
var color = require("color")
var reduceFunctionCall = require("reduce-function-call")

function reduceHwb(body) {
  return color("hwb(" + body + ")").rgb().string()
}

/**
 * PostCSS plugin to transform hwb() to rgb()
 */
module.exports = postcss.plugin("postcss-color-hwb", function() {
  return function(style) {
    style.walkDecls(function transformDecl(decl) {
      if (!decl.value || decl.value.indexOf("hwb(") === -1) {
        return
      }

      decl.value = helpers.try(function transformHwb() {
        return reduceFunctionCall(decl.value, "hwb", reduceHwb)
      }, decl.source)
    })
  }
})