background-transparency.styl

// source: https://gist.github.com/adunkman/2580972

// background transparency
background-transparency(hexColor, alpha = 1)
  ms-color = argb(hexColor, alpha)
  background hexToRgb(hexColor)
  background rgba(hexColor, alpha)
  .mod-no-rgba &
    *zoom 1
    background transparent
    filter s('progid:DXImageTransform.Microsoft.gradient(startColorstr=%s,endColorstr=%s)', ms-color, ms-color)
    &:nth-child(n)
      filter none

// convert a decimal to hex 
hex(decimal)
   hex-value = ('0') ('1') ('2') ('3') ('4') ('5') ('6') ('7') ('8') ('9') ('A') ('B') ('C') ('D') ('E') ('F')
   unquote(hex-value[floor(decimal / 16)] + hex-value[floor(decimal % 16)])

// convert to old 8-digit MS hex value where first 2 digits are the Alpha hex value 
argb(color, alpha = 1)
  s('#%s%s', hex(alpha * 255), color)

// convert hex colors to RGB
hexToRgb(hexColor)
  s('rgb(%s, %s, %s)', red(hexColor), green(hexColor), blue(hexColor))