色值转换

module.exports = {

  /**
   * hex to rgb
   * @param  {String} hex 十六进制的颜色表达方式
   * @return {Object} rgb
   */
  hex2rgb: function(hex) {
    if (hex.charAt(0) === '#') {
      hex = hex.substr(1)
    }

    if (hex.length === 3) {
      hex = hex.substr(0, 1) + hex.substr(0, 1) + hex.substr(1, 2) + hex.substr(1, 2) + hex.substr(2, 3) + hex.substr(2, 3)
    }

    return {
      r: parseInt((hex.charAt(0) + '' + hex.charAt(1)), 16),
      g: parseInt((hex.charAt(2) + '' + hex.charAt(3)), 16),
      b: parseInt((hex.charAt(4) + '' + hex.charAt(5)), 16),
      a: 1
    }
  },

  /**
   * hex to hsl
   * @param  {String} hex 十六进制字符串
   * @return {Object} hsl
   */
  hex2hsl: function(hex) {
    return this.rgb2hsl(this.hex2rgb(hex))
  },

  rgb2hsl: function(rgb) {
    let r = rgb.r / 255,
      g = rgb.g / 255,
      b = rgb.b / 255,
      a = rgb.a,
      max = Math.max(r, g, b),
      min = Math.min(r, g, b),
      h,
      s,
      l = (max + min) / 2,
      d

    if (max == min) {
      h = s = 0
    } else {
      d = max - min
      s = l > 0.5 ? d / (2 - max - min) : d / (max + min)

      if (max == r) {
        h = (g - b) / d
      } else if (max == g) {
        h = (b - r) / d + 2
      } else {
        h = (r - g) / d + 4
      }

      h *= 60
    }

    return {
      h: h,
      s: s,
      l: l,
      a: a
    }
  },

  /**
   * rgb to hex
   * @param  {Object} rgb
   * @return {String}
   */
  rgb2hex: function(rgb) {
    function hex(x) {
      return ('0' + parseInt(x).toString(16)).slice(-2)
    }
    return '#' + hex(rgb.r) + hex(rgb.g) + hex(rgb.b)
  },

  /**
   * hsl to hex
   * @param  {Object} hsl
   * @return {String}
   */
  hsl2hex: function(hsl) {
    return this.rgb2hex(this.hsl2rgb(hsl))
  },

  /**
   * hsl to rgb
   * @param  {Object} hsl
   * @return {Object}
   */
  hsl2rgb: function(hsl) {
    let h = hsl.h,
      s = hsl.s,
      l = hsl.l,
      a = hsl.a,
      r,
      g,
      b,
      p,
      q,
      m

    h /= 60
    if (h < 0) {
      h = 6 - (-h % 6)
    } else {
      h %= 6
    }

    p = (1 - Math.abs((2 * l) - 1)) * s
    q = p * (1 - Math.abs((h % 2) - 1))

    if (h < 1) {
      r = p
      g = q
      b = 0
    } else if (h < 2) {
      r = q
      g = p
      b = 0
    } else if (h < 3) {
      r = 0
      g = p
      b = q
    } else if (h < 4) {
      r = 0
      g = q
      b = p
    } else if (h < 5) {
      r = q
      g = 0
      b = p
    } else {
      r = p
      g = 0
      b = q
    }

    m = l - p / 2
    r = Math.round((r + m) * 255)
    g = Math.round((g + m) * 255)
    b = Math.round((b + m) * 255)

    return {
      r: r,
      g: g,
      b: b
    }
  },
}