Re: convert image to greyscale (color to black and white)

[liz]

my $g = ( $c[0] + $c[1] + $c[2] ) / 3; # Color::Calc::grey

Although this is the way in which Color::Calc::grey works, I wonder whether this will produce the best black and white version of a color image. This is because the human eye is differently sensitive to different colours (e.g. more sensitive to red, which is why traffic lights are red, or so I'm told).

I don't have another formula to be used at hand, just pointing out something that may warrant some further investigation.

Liz

[tachyon]

Actually the eye is most sensitive to GREEN which is why all the night vision stuff is always green light. The best formula (according to the GIMP guys is the proportional luminescence one - see Re: convert image to greyscale (color to black and white)

[Razorbeard]

May I suggest that the reason that green is used for night lighting isnt so much the eye sensitivity, tho that IS true. It has to do with persistance of vision. Green can be easily seen at night while preserving your night vision. Brighter colors like yellow kinda mess-up your night vision. Green is more "friendly" to your night vision. Some car instrument panels (speedometer, etc) are lit in yellow. While that is easier to see it is hard on your night vision. This may not be true for everybody, but it is generally true for most people.