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Nine Shades of Greyscale
Nine different formulas for greyscale.
Set a colour using the sliders, this is then converted to greyscale using each of nine formulas, and you can see each colour’s brightness (i.e. greyscale) value from the chart.
255 255 255   Base Colour
  There is a more detailed implementation of this page at
Web Hex:
Greyscales
255
200
100
 
000
STW*
000
gXYZ
000
gYIQ
000
sXYZ
000
sYIQ
000
 XYZ
000
 YIQ
000
 Lgt
000
 Avg
There are different ways to calculate greyscale from a colour. They all work well for different jobs, horses for courses, and very badly for other jobs. Generally, looking at a photo converted to greyscale, it’s nigh-on impossible for the eye to tell the difference, but significant when defining text and manipulating photos.
Key:
STW*The SEEMS TO WORK formula devised by me and described on Readable Text in Colour – STW*.
gXYZInverse gamma using the XYZ coefficients of R: 0.212655, G: 0.715158 and B: 0.072187, inverse gamma as described on StackOverflow.
sYIQInverse gamma using the YIQ coefficients of R: 0.299, G: 0.587, B: 0.114, YIQ coefficients also known as Digital CCIR601.
sXYZSquare root using the XYZ coefficients: sqrt((0.212655*(R^2)) + (0.715158*(G^2)) + 0.072187*(B^2)).
sYIQSquare root using the YIQ coefficients: sqrt((0.299*(R^2)) + (0.587*(G^2)) + (0.114*(B^2)).
XYX0.212655*R + 0.715158*G + 0.072187*B, also known as the Luminosity formula, see Puzzling Greys.
YIQ0.299*R + 0.587*G + 0.114*B, as in the Web Accessibility Guidelines from the W3C, see Holes in the W3C Colour Readability Guidelines.
LgtLightness: ½ × (max(R,G,B) + min(R,G,B)), see Puzzling Greys.
AvgAverage:(R + G + B) ÷ 3, see Puzzling Greys.
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This page is now to be found at landofinterruptions.co.uk/nineshades

 
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