Hi @go-go-go,
Those terms should be correct for the last stable GIMP:
; YCbCr ITU R470 256
(define tmp (plug-in-decompose 1 Image Drawable "YCbCr ITU R470 256" 0))
(define lyr (gimp-layer-new-from-drawable ( car( gimp-image-get-active-layer (car tmp) )) Image) )
(gimp-item-set-name (car lyr) "Luma - y470f")
(gimp-image-add-layer Image (car lyr) -1)
; YCbCr ITU R709 256
(define tmp (plug-in-decompose 1 Image Drawable "YCbCr ITU R709 256" 0))
(define lyr (gimp-layer-new-from-drawable ( car( gimp-image-get-active-layer (car tmp) )) Image) )
(gimp-item-set-name (car lyr) "Luma - y709f")
(gimp-image-add-layer Image (car lyr) -1)
From the PDB explorer:
decompose-type STRING
What to decompose: "RGB", "Red", "Green", "Blue", "RGBA",
"HSV", "Hue", "Saturation", "Value", "HSL", "Hue (HSL)",
"Saturation (HSL)", "Lightness", "CMY", "Cyan", "Magenta",
"Yellow", "CMYK", "Cyan_K", "Magenta_K", "Yellow_K",
"Alpha", "LAB", "YCbCr_ITU_R470", "YCbCr_ITU_R709",
"YCbCr ITU R470 256", "YCbCr ITU R709 256"