Graff desaturation

Getting help
Bar Welt

Graff desaturation

Postby Bar Welt » Tue Oct 13, 2009, 14:37

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 ?

User avatar
Creator
Posts: 157
Joined: Tue Dec 16, 2008, 20:52
Location: Hannover, Germany
Contact:

Re: Graff desaturation

Postby Creator » Tue Oct 13, 2009, 17:16

Currently we use the following desaturation algorithm: C = (R + G + B) / 3.
Before committing a bug, I suggest to discuss desaturation here.

Administrator
Site Admin
Posts: 20
Joined: Tue Dec 16, 2008, 20:29
Contact:

Re: Graff desaturation

Postby Administrator » Tue Oct 13, 2009, 23:20

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.

User avatar
Creator
Posts: 157
Joined: Tue Dec 16, 2008, 20:52
Location: Hannover, Germany
Contact:

Re: Graff desaturation

Postby Creator » Tue Jan 26, 2010, 02:39

The difference can be illustrated here:
face_org_3.jpg
Original Photo
face_org_3.jpg (8.72 KiB) Viewed 11748 times
face_bw_3.gif
Desaturated Photo
face_bw_3.gif (71.81 KiB) Viewed 11748 times

User avatar
Creator
Posts: 157
Joined: Tue Dec 16, 2008, 20:52
Location: Hannover, Germany
Contact:

Re: Graff desaturation

Postby Creator » Tue Jan 26, 2010, 12:39

Maybe it will be better example:
color_table_org.jpg
color_table_org.jpg (17.78 KiB) Viewed 11743 times

color_table_4.gif
color_table_4.gif (72.81 KiB) Viewed 11743 times

User avatar
Creator
Posts: 157
Joined: Tue Dec 16, 2008, 20:52
Location: Hannover, Germany
Contact:

Re: Graff desaturation

Postby Creator » Tue Jan 26, 2010, 16:36

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.


Return to “Support”

Who is online

Users browsing this forum: No registered users and 0 guests