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Graff desaturation

Posted: Tue Oct 13, 2009, 14:37
by Bar Welt
Hallo. I use Graff 1.0.24, and it looks like the desaturation algorithm performs not properly. I just compared the desaturated image with the same image after the desaturation in GIMP. Should I commit the bug report on that ?

Re: Graff desaturation

Posted: Tue Oct 13, 2009, 17:16
by Creator
Currently we use the following desaturation algorithm: C = (R + G + B) / 3.
Before committing a bug, I suggest to discuss desaturation here.

Re: Graff desaturation

Posted: Tue Oct 13, 2009, 23:20
by Administrator
Photoshop uses the following approach. In the gray value of the pixel should the luminance be written. It is calculatd as average sum of the maximal and minimal color channel values.

Re: Graff desaturation

Posted: Tue Jan 26, 2010, 02:39
by Creator
The difference can be illustrated here:
face_org_3.jpg
Original Photo
face_org_3.jpg (8.72 KiB) Viewed 11403 times
face_bw_3.gif
Desaturated Photo
face_bw_3.gif (71.81 KiB) Viewed 11403 times

Re: Graff desaturation

Posted: Tue Jan 26, 2010, 12:39
by Creator
Maybe it will be better example:
color_table_org.jpg
color_table_org.jpg (17.78 KiB) Viewed 11398 times

color_table_4.gif
color_table_4.gif (72.81 KiB) Viewed 11398 times

Re: Graff desaturation

Posted: Tue Jan 26, 2010, 16:36
by Creator
Starting from the version 1.0.30d we have corrected the Desaturate function. Now it produces the same result as in Adobe Photoshop. Basically this function, now uses the Hue/Saturation functionality, i.e C = [Min(R, G, B) + Max(R, G, B)] / 2.
To achive old result, i.e. C = [R + G + B] / 3, please use function Black & White with default settings.