GraphicsUnit的6个枚举值分别都在什么情况下使用？

[weixin_44591510]

//
// 摘要:
// Specifies the unit of measure for the given data.
public enum GraphicsUnit
{
Display = 1,
Pixel = 2,
Point = 3,
Inch = 4,
Document = 5,
Millimeter = 6
}