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Applying 16 bit curves on import

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Applying 16 bit curves on import Edward Coffey 17 Nov 12:22
  Applying 16 bit curves on import Martin Nordholts 17 Nov 20:31
Edward Coffey
2008-11-17 12:22:44 UTC (about 16 years ago)

Applying 16 bit curves on import

Hi all,

Since (if I understand correctly) the color adjustment tools in GIMP have been updated to use GEGL, would it be viable to introduce an optional 16 bit color-correction stage to the import of 16 bit images? Specifically, a curves dialog, perhaps including saturation. If it's possible to implement without a great deal of time and effort, this might be a shortcut to provide the kind of 16 bit support that will actually benefit photo-editors (particularly those dealing with scanned film, rather than digital where most of these large-scale color adjustments where high bit-depth actually makes a difference are possible in pre-processing tools like UFRaw).

Cheers, Ed.

Martin Nordholts
2008-11-17 20:31:40 UTC (about 16 years ago)

Applying 16 bit curves on import

Edward Coffey wrote:

Hi all,

Since (if I understand correctly) the color adjustment tools in GIMP have been updated to use GEGL, would it be viable to introduce an optional 16 bit color-correction stage to the import of 16 bit images?

Hi!

Not without quite a bit of effort. The point of porting stuff to GEGL is indeed to make such things possible, but in the current code the image data is compressed to 8-bit per channel already in the loading-from-file phase (at least for 16 bpc .pngs), i.e. before we have a chance to use any colour adjustment tools on the data.

In order to support the above one would have to at least

1. Extend the plug-in API to deal with high bit-depth images 2. Adapt the core to store the high bit-depth data 3. Adapt the core to pass the high bit-depth data to the colour adjustment tools.

The only thing you "get for free" is that the colour tools already do their processing in 32-bit per channel linear light RGBA, so if you manage to give them high bit-depth data they can handle that.

Note that in GIMP trunk the projection construction code, i.e. the code that combines layers into a single image, is as good as ported to GEGL too. Support for high bit-depth and non-destructive editing is in other words closer than ever, but there's still a lot to do.

BR, Martin