Specified what color components are present in an archetypes.Image.
This combined with datatypes.ChannelDatatype determines the pixel format of an image.
Variants
L = 1
Grayscale luminance intencity/brightness/value, sometimes called Y
RGB = 2
Red, Green, Blue
RGBA = 3
Red, Green, Blue, Alpha
BGR = 4
Blue, Green, Red
BGRA = 5
Blue, Green, Red, Alpha
Arrow datatype
UInt8