[Bug-ocrad] reading color images

[Erik Auerswald]

Hi,

I've noticed that GNU Ocrad 0.14 implements reading of color images and
looked at the code (without testing it). You seem to use the formula

greyvalue = min(red, green, blue)

which does not at all work like the human eye. I would recommend using
one of the following two formulas:

greyvalue = 0.2125*red + 0.7154*green + 0.0721*blue
greyvalue = 0.299*red + 0.587*green + 0.114*blue

To see the results of these formulas take a look at
http://www.unix-ag.uni-kl.de/~auerswal/ssocr/greyscale.html
(contains about 1.4 MB of image data).

For information about color specification in images see the color FAQ at
http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html

Regards,
Erik

P.S. I'm not subscribed to this list, so please cc: me if you want to
answer me.