RGB <=> YCbCr(YPbPr) color space conversion

yuvrgb.md

Y  = a * R + b * G + c * B
Cb = (B - Y) / d
Cr = (R - Y) / e

	BT.601	BT.709	BT.2020
a	0.299	0.2126	0.2627
b	0.587	0.7152	0.6780
c	0.114	0.0722	0.0593
d	1.772	1.8556	1.8814
e	1.402	1.5748	1.4746

R = Y + e * Cr
G = Y - (a * e / b) * Cr - (c * d / b) * Cb
B = Y + d * Cb

• https://www.itu.int/rec/R-REC-BT.601
• https://www.itu.int/rec/R-REC-BT.709
• https://www.itu.int/rec/R-REC-BT.2020

Color spaces are the most niche, rabbit holey thing ever, I swear

They really are. I feel I will never gain my time back from learning this stuff.

e for BT.2020 should be 1.4746, it can be calculated by the following formula:
e = (1 - a) / 0.5,
d = (1 - c) / 0.5

e for BT.2020 should be 1.4746,

Fixed. thanks!

Looks like Cb/Cr should be centred around 0.5?

Y  = a * R + b * G + c * B
Cb = (B - Y) / d  + 0.5
Cr = (R - Y) / e + 0.5

Chrominance(Chroma) Cb/Cr are defined in the range [-0.5, 0.5].

Oh yup, my bad, I was thinking about it for use in a shader.

Golang code for those interested

type BT struct {
	A float64
	B float64
	C float64
	D float64
	E float64
}

var (
	BT601  = BT{A: 0.299, B: 0.587, C: 0.114, D: 1.772, E: 1.402}
	BT709  = BT{A: 0.2126, B: 0.7152, C: 0.0722, D: 1.8556, E: 1.5748}
	BT2020 = BT{A: 0.2627, B: 0.6780, C: 0.0593, D: 1.8814, E: 1.4746}
)

func RgbToYCbCr(r, g, b float64, space BT) (y, cb, cr float64) {
	y = space.A*r + space.B*g + space.C*b
	cb = (b - y) / space.D
	cr = (r - y) / space.E
	return
}

func YCbCrToRgb(y, cb, cr float64, space BT) (r, g, b float64) {
	r = y + space.E*cr
	g = y - (space.A*space.E/space.B)*cr - (space.C*space.D/space.B)*cb
	b = y + space.D*cb
	return
}

where the hellyante skibidi sigma is the srgb to ycbcr

ong ts is actually goated, only took me around 6, 7 tries to get right