ColorTypes
ColorTypes 引入了一系列色彩相关的类型，其底层使用了 FixedPointNumbers 包优化
julia> c=RGB(0.5,0.5,0.5)
RGB{Float64}(0.5,0.5,0.5)
julia> red(c) # 或 c.r
0.5
julia> c=RGBA(1,1,0,0)
RGBA{N0f8}(1.0,1.0,0.0,0.0)
julia> alpha(c)
0.0N0f8
julia> alpha(c).i
0x00
在 0.11.0 使用 typetree 生成的类型层次树如下：
Colorant
| Color
| | AbstractRGB
| | | BGR
| | | RGB
| | | RGB24 m
| | | RGBX
| | | XRGB
| | DIN99
| | DIN99d
| | DIN99o
| | Gray
| | Gray24 m
| | HSI
| | HSL
| | HSV
| | LCHab
| | LCHuv
| | LMS
| | Lab
| | Luv
| | XYZ
| | YCbCr
| | YIQ
| | xyY
| TransparentColor
| | AlphaColor
| | | ABGR
| | | ADIN99
| | | ADIN99d
| | | ADIN99o
| | | AGray
| | | AGray32 m
| | | AHSI
| | | AHSL
| | | AHSV
| | | ALCHab
| | | ALCHuv
| | | ALMS
| | | ALab
| | | ALuv
| | | ARGB
| | | ARGB32 m
| | | AXYZ
| | | AYCbCr
| | | AYIQ
| | | AxyY
| | ColorAlpha
| | | BGRA
| | | DIN99A
| | | DIN99dA
| | | DIN99oA
| | | GrayA
| | | HSIA
| | | HSLA
| | | HSVA
| | | LCHabA
| | | LCHuvA
| | | LMSA
| | | LabA
| | | LuvA
| | | RGBA
| | | XYZA
| | | YCbCrA
| | | YIQA
| | | xyYA