Bug 224682

Summary: Color Channel Mixer ui & usability
Product: [Applications] digikam Reporter: Jens Mueller <tschenser>
Component: Plugin-Editor-ChannelsAssignee: Digikam Developers <digikam-bugs-null>
Status: RESOLVED NOT A BUG    
Severity: normal    
Priority: NOR    
Version: 1.1.0   
Target Milestone: ---   
Platform: Ubuntu   
OS: Unspecified   
Latest Commit: Version Fixed In: 1.1.0
Sentry Crash Report:

Description Jens Mueller 2010-01-28 22:39:47 UTC 
Version:           1.1 svn (using KDE 4.3.4)
Installed from:    Ubuntu Packages

When using colour channel mixer tool I discovered the following behaviour:
1. open tool, red histogram channel should be selected with the given values of red:100, green: 0, blue: 0
2. I push the reset button behinds the red value box
3. red is zero now, ok this can easially be fixed

Next if you select another histogram channel, for example green the green slider and box gets a value of 100 and blue and red 0. Not understandable to the user why values change when you only change the view of histogram. Also, why can I have different values for blue when switching between red and green histogram channel? BTW, to which unit do the values align?

And the last question: What is the big difference between colour channel mixer tool and colour balance tool? For me this looks only like two guis for the same image operation, right?

Jens
Comment 1 caulier.gilles 2010-01-29 08:38:52 UTC 
Channel Mixer is generally a tool to mix channel together and make black and white images.

I have used histogram channel combo to setup mixer chanel, to not duplicates settings here. Try gimp channel mixer tool to compare. The code is ported from gimp to digiKam with 16 bits color depth support.

Gilles Caulier
Comment 2 Jens Mueller 2010-01-29 19:27:36 UTC 
Yes Gilles, Gimp behaves the same. It's perfect to do black & white images, but I do still not understand why there are different settings per channel (gimp also). I have to dive deeper in this. A the moment channel mixer tool makes only sense with monochrome option always on for me.

As I mentioned colour balance tool: gimp can do it with hightlights|midtones| shadows and has also a preserve luminosity option. It would be nice to have this also in digikam, do you think so?

Jens
Comment 3 Johannes Wienke 2010-01-29 20:21:27 UTC 
With the channel mixer you can also change the brightness of the image and also use a channel as a weighted subtraction whereas the balance tool doesn't allow this and has another focus.
Comment 4 Jens Mueller 2010-01-30 10:12:26 UTC 
Yes Johannes, weihtened subtraction is the keyword. Most of this entry is invalid. If I think about, everythink is clear. But perhaps we can make things more clear for beginners. Some suggestion would be to rename the "channel" label to "mix channel" or "ouput channel" as gimp. But "output channel" is not the best, as the top right histogram is always output. Another option would be to have a second "mix channel" drop down box between histogram and mixer sliders and make histogram independent of shown mixer settings. Then we can also add a "colours entry" to the histogram channel drop down box.

What do you think about?

Jens
Comment 5 Jens Mueller 2010-01-30 11:31:10 UTC 
SVN commit 1082351 by jmueller:

make the single channel reset toolbuttons work to point to per channels defaults
CCBUGS: 224682

 M  +12 -0     channelmixertool.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1082351