On Sun, Aug 2, 2009 at 7:49 PM, SHIRAKAWA Akira <shirakawa.akira@xxxxxxxxx> wrote:
LCH processing is definitely slower than HSV or HSL (whether optimized or not), so this may have an impact on display update speed (and consequently on user experience)
There are a few different ways of applying a 'Color' like operation, varying in quality and speed.
LCH is certainly the best quality, Yiq is lesser quality but faster, HSL is even lesser quality and very fast, HSV is the fastest (but so inaccurate it's laughable)
Since GEGL provides a number of operations that are inherently expensive (eg bilateral-filter), it may be worth considering the idea of graphs with quality controls built in. For example, while you are painting on your Color layer, it switches from paint application using LCH to Yiq (which is a nice compromise and has been used for heavy-duty tasks with good results -- see http://www.cs.huji.ac.il/~yweiss/Colorization/).
When you stop painting, it updates with the actual LCH results.
This would allow more responsive painting (and could also be applied to paint modes)
Martin: I have made use of GIMP Value mode in the esoteric kind of way you mention. I agree it is not worthwhile to support such uses (imo more like abuses -- this kind of use is really begging for the use of PIL or NumPy on a chunk of image, not the application of an image *editor*)
Martin Nordholts wrote:I very rarely use layer modes (and I'm not a GIMP hacker so I'm probably
> Does anyone see any problems with using CIE LCH instead of HSV for these
> layer modes? We can ignore backwards compatibility issues for now.
missing something), but if using internally CIE LCH for image processing
instead of HSV leads to more correct results, then I wouldn't see any
reason to not use it.
Except for the final results, will there be any change at a user
interaction level? Or any practical drawback resulting from this?
LCH processing is definitely slower than HSV or HSL (whether optimized or not), so this may have an impact on display update speed (and consequently on user experience)
There are a few different ways of applying a 'Color' like operation, varying in quality and speed.
LCH is certainly the best quality, Yiq is lesser quality but faster, HSL is even lesser quality and very fast, HSV is the fastest (but so inaccurate it's laughable)
Since GEGL provides a number of operations that are inherently expensive (eg bilateral-filter), it may be worth considering the idea of graphs with quality controls built in. For example, while you are painting on your Color layer, it switches from paint application using LCH to Yiq (which is a nice compromise and has been used for heavy-duty tasks with good results -- see http://www.cs.huji.ac.il/~yweiss/Colorization/).
When you stop painting, it updates with the actual LCH results.
This would allow more responsive painting (and could also be applied to paint modes)
Martin: I have made use of GIMP Value mode in the esoteric kind of way you mention. I agree it is not worthwhile to support such uses (imo more like abuses -- this kind of use is really begging for the use of PIL or NumPy on a chunk of image, not the application of an image *editor*)
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