[Digikam-devel] [Bug 128377] Adjust levels: histograms don't match, bad "auto level" function

[Gilles Caulier]

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http://bugs.kde.org/show_bug.cgi?id=128377         




------- Additional Comments From caulier.gilles gmail com  2008-03-25 20:19 -------
Let's me comment point #1 :

the original histogram is _always_ computed from _original_ image, never from preview. There is no performance problem here, because original histogram is always computed one time, at plugin startup...

The only histogram which is computed in live is about target image, and of course for performance reason. Computing full target image histogram is a non-sence : this require to render all color changes to original image and compute histogram as well. For large image, this will take a time and plugin will not be suitable duing time latencies (i'm sure, i have verified this point when i have developped DigikamImagePlugins in the past (:=)))

But, there is one point which can be improved here : all Color correction tools (CurvesAdjust, HistogramAdjust, WhiteBalance, ColorMixer, etc...) render target image on main digiKam thread not using a separated thread as all others image plugins (SharpnessEditor, Restoration, etc...). If we use multithreading here, render can be forked to another cpu and plugins can be more suitable in live, but this will not work better with mono-cpu computers.

Note : Unforget than Target Histogram computed from preview image is just a guide to help photographer.

Gilles Caulier