Hello, I just mention who a constrast can be better with using soft clipping equations. If you just apply a linear correction you can insert clamped values. Using curves like: http://www.luminous-landscape.com/forum/index.php?topic=52364.0 y = x^2*2 for x<=0.5 y = 1-(1-x)^2*2 for x>0.5
can offer contrast adjustment without clipping values. But I don't know if it's the goal of OpenImageIO to add these process. I think it could be better if it only a library to opening/writing files, others projects can used this project to apply effects. 2012/7/24 Stefan Stavrev <[email protected]> > Just a reminder, I am working on manual contrast that > applies this formula to all pixels: > out = (in - pivot) * contrast + pivot > > I propose this API: http://ideone.com/thm5e > > and this usage: > > 1. ./oiiotool in.png --contrast contrast -o out.png > This applies the formula to all channels, and assumes > pivot = 0.5(average of 0 and 1), which is mostly used. > > If you want to specify pivot then: > ./oiiotool in.png --contrast:pivot=0.3 contrast -o out.png > > 2. ./oiiotool in.png --contrast:rgb=1 contrast -o out.png > This means we have RGB image as input and the formula > is applied to the luminance channel rather than all channels, > which leads to better results. > > If we want to specify pivot then: > ./oiiotool in.png --contrast:rgb=1:pivot=0.3 contrast -o out.png > > So, if the user wants to apply the contrast method to all channels > he can use option 1). If for RGB images he wants better results, > he can use 2). I expect pivot to be rarely changed, the default 0.5 > will be good enough for many cases. > > > > > _______________________________________________ > Oiio-dev mailing list > [email protected] > http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org > > -- Marc-Antoine* *ARNAUD Software Engineer Mikros Image - Digital Post-Production for Video and Film www.mikrosimage.eu
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