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Re: Introduction to GEGL Buffers

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Let me try to be a bit more specific, one issue at a time.

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I agree that, at least at low order (which is all we're doing for
now), abyss policies are independent of whether we are using the
"center" or "corner" image conventions, and are also independent of
whether we are implementing an exact area method (like most
implementations of box filtering), or a point resampler (like standard
bicubic).

However, Øyvind expressed a desire to have something implemented in or
for the resamplers which cannot really be done with the usual abyss
policy implementations.

Here is:

Associate a "default" constant colour with a buffer. What Øyvind would
like (if I understand correctly) is that instead of sampling through
the implied boundary using the resampler as if there was no boundary
(filling in the missing footprint values using the abyss policy), the
resampled values "drop dead" at the boundary and from then on are
filled (filled, not blended) with the default colour. For example, the
sampler could use the nearest neighbour abyss policy (a.k.a. clamp)
for requested values up to the boundary line, and return the default
colour past it.

Comment: Thinking about this some more, I am starting to think that it
is a bad idea to implement this. (Later.)

Irregardless of whether this is a good or bad idea, the main point is:

Where should the "drop dead" transition occur:

Aligned with the (center of) the boundary pixels? Or half a pixel
width out (at the boundary of the pixel area associated with boundary
pixels)?

One of my worries is that if one when doing something else than
resizing this will essentially behave like nearest neighbour (from the
outside in), which will be ugly.  So, >>I<< am actually starting to
think that "drop dead" is not such a good idea.

But I'd love to hear opinions on this.

nicolas

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