对于阴影，将每个分量乘以1/4，1/2，3

• For shades, multiply each component by 1/4, 1/2, 3/4, etc. of its previous value, depending on how dark the color should be.

  对于色调，计算（255 - 上一个值） ），将它乘以1/4，
  1/2，3/4等，并将其与上一个值相加。

  For tints, calculate (255 - previous value), multiply that by 1/4, 1/2, 3/4, etc. and add that to the previous value.