Re: [Gegl-developer] [Gimp-developer] babl roadmap

[Øyvind Kolås <pippin gimp org>]

On Wed, Oct 15, 2014 at 2:11 PM, Elle Stone
> When the user opens a color-managed fooRGB image, for which *specific*
> editing operations will the image be converted to unbounded sRGB?
>
> This isn't just an implementation detail. The answer to this question will
> determine the path for writing code going forward. To restate the question
> yet again:

If the user is putting a text-layer, which has been rendered using
cairo and is in 8bit sRGB premultiplied alpha. The compositing of this
with preceding data in the layer stack the babl-format of the output
buffer of the over/normal compositing operation, as well as the data
fetched from both buffer inputs - would likely be RaGaBaA float - if
the two linear inputs differ.

At all points we know the CIE Lab or XYZ coordinates of all involved
pixels – and we aim to do as few conversions as possible (never
converting the actual data to either bablRGB or XYZ, even temporarily
- unless requested.)

> Will all color-managed image editing be done using the user's chosen
> primaries, with absolutely no conversions to unbounded sRGB for image
> editing?
>
> Or are the developers committing themselves to maintaining lists of which
> operations should be done using fooRGB primaries and which should be done
> using sRGB primaries?

There is no plan to maintain lists in the end, this information would
be self-contained within each individual operation, like whether the
operation needs CIE Lab, pre-multiplied alpha or not or even an 16bit
linear grayscale. This automatic data representation conversion is an
inherent abstraction and property both of GeglBuffer and the services
provided for op authors to make implementing consistently behaving
operations easy.

/Ø