On Tue, 21 Jan 2003 18:48:39 -0800, larry@marso.com said:

The default histogram display seems wrong in Gimp, by the standards of photoshop and a number of other image management programs. There is a link below to an image demonstrating what I mean. (I am cross-posting this to Filmgimp, because there seems to be common histogram code).

An optional plug-in for Gimp called "Color Correction" seems to do histograms the way I would expect, i.e., giving meaningful feedback to determine (about a photograph) whether the exposure was well chosen, and serving as a useful guide for correction using levels and curves.

Take a look at this image to see how Gimp's main histogram display compares with the Color Correction plug-in's.

http://www.marso.com/images/example.jpg

This is something I brought up some time ago (see http://lists.xcf.berkeley.edu/lists/gimp-developer/2001-February/004518.html). The Gimp uses logarithmic scaling, while other image processing tools I know use another kind of scaling -- I thought linear, but sqrt has also been suggested.

At first I didn't like the way the Gimp does it, because I think it doesn't look pretty. But then I started to think that logarithmic scaling actually isn't so bad for these kinds of things.

Best regards, Roel Schroeven

Hi,

hw18qzv02@sneakemail.com writes:

Take a look at this image to see how Gimp's main histogram display compares with the Color Correction plug-in's.

http://www.marso.com/images/example.jpg

This is something I brought up some time ago (see http://lists.xcf.berkeley.edu/lists/gimp-developer/2001-February/004518.html). The Gimp uses logarithmic scaling, while other image processing tools I know use another kind of scaling -- I thought linear, but sqrt has also been suggested.

At first I didn't like the way the Gimp does it, because I think it doesn't look pretty. But then I started to think that logarithmic scaling actually isn't so bad for these kinds of things.

see also http://bugzilla.gnome.org/show_bug.cgi?id=72951. Would be nice to get this into 1.4 but we'd need a volunteer pretty soon now.

Salut, Sven

hw18qzv02@sneakemail.com writes:

The Gimp uses logarithmic scaling, while other image processing tools I know use another kind of scaling -- I thought linear, but sqrt has also been suggested.

Sven Neumann writes:

see also http://bugzilla.gnome.org/show_bug.cgi?id=72951. Would be nice to get this into 1.4 but we'd need a volunteer pretty soon now.

I took a stab at it, and attached a patch to the bug. I only did linear, but now that I know where the code goes, it would be trivial to add sqrt or other scalings if anyone thought they would be useful.

My patch only affects the display of the histogram, not any calculations. Should it affect anything besides the display?

...Akkana