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Greyscale Conversions
Select picture
or specify image url apply
will be converted to 500px × 375px
 
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Click anywhere the colour picture to select a colour. Move the mouse to change selection, click again to stop colour change on mouse move.
Selected
 
STW*
 
W3C YIQ
 
CIE XYZ
 
Lgt’ness
 
Average
 
The above boxes show the selected colour (on mouse click or mouse move) converted to greyscale by each of five different formulas (formulas explained underneath the set of pictures).
You’ll see that for a given hue different formulas produce different greyscale, this is particularly so on yellowy colours for some reason, yet in the converted photos, you barely notice it. That is (presumably) because you see the shades in a photo relatively, not absolutely.
It also indicates that when converting a complex photo to greyscale it does not matter much which formula you use, but when looking at text over a background, it will matter more.
STW*
W3C YIQ
CIE XYZ
Lightness
Average
Each panel shows the colour photo converted to greyscale according to one of five formulas for converting to brightness.
STW* is the formula devised by me, and discussed in detail on Readable Text in Colour – STW*.
W3C YIQ is the YIQ formula recommended by the W3C and discussed on Holes in the W3C Colour Readability Guidelines.
The formulas for other three: CIE XYZ, Lightness and Average, can be found on Puzzling Greys.
 
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This page is now to be found at landofinterruptions.co.uk/greyscale-conversion

 
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