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Wilbert · 2nd January 2005, 15:40

I'm so confused

Regarding Graft's hue filter. The saturation setting does the following. Setting it to one leaves the rgb clip untouched, and setting it to zero sets the rgb clip to (r,g,b)=(y,y,y) where y is the luminance (as in yuv). In [0,1] it just performs a linear interpolation (and linear extrapolation outside [0,1]).

Normally we have y = 0.299*r + 0.587*g + 0.114*b, but they use a gamma-corrected version: y = 0.3086*r + 0.6094*g + 0.0820*b (don't know yet where these numbers are coming from ...).

http://www.sgi.com/misc/grafica/matrix/index.html

What I don't understand is, how is this related to the saturation in the hsv color format? I guess there's no relation? Setting the saturation to zero results in (r,g,b) = (V,V,V) with V = max(r,g,b) and setting it to one the (r,g,b) may or may not change.

2nd January 2005, 15:40	#29 \| Link
Wilbert Moderator Join Date: Nov 2001 Location: Netherlands Posts: 6,364	I'm so confused Regarding Graft's hue filter. The saturation setting does the following. Setting it to one leaves the rgb clip untouched, and setting it to zero sets the rgb clip to (r,g,b)=(y,y,y) where y is the luminance (as in yuv). In [0,1] it just performs a linear interpolation (and linear extrapolation outside [0,1]). Normally we have y = 0.299r + 0.587g + 0.114b, but they use a gamma-corrected version: y = 0.3086r + 0.6094g + 0.0820b (don't know yet where these numbers are coming from ...). http://www.sgi.com/misc/grafica/matrix/index.html What I don't understand is, how is this related to the saturation in the hsv color format? I guess there's no relation? Setting the saturation to zero results in (r,g,b) = (V,V,V) with V = max(r,g,b) and setting it to one the (r,g,b) may or may not change. Last edited by Wilbert; 2nd January 2005 at 17:47.