Re: [Gimp-developer] Warp transform Abyss policy

On Tue, Jun 13, 2017 at 04:06:09PM -0400, Ell via gimp-developer-list wrote:
On Tue, 13 Jun 2017 18:39:39 +0200
Julien Hardelin <jm hard wanadoo fr> wrote:

Hello developers,

I am writing gimp-help-2 doc for warp transform tool and I have 
difficulty with "Abyss policy". I read the wiki/glossary for these
items but did not understand what they do.

How to explain these features to users?

Granted, the abyss policy option is a bit on the technical side.

The warp tool moves pixels from one point to another.  Some pixels may
come from outside the layer boundary.  These pixels don't actually
exist anywhere, and therefore don't have any associated color; yet, we
must assign *some* color to them.  The abyss policy specifies how to
determine their color:

  - None:  Assume that all pixels outside the layer boundary are

  - Clamp:  Assume that each edge of the layer stretches out
    indefinitely, so, for example, a pixel to the left of the layer
    boundary has the same color as the leftmost pixel of the layer with
    the same y coordinate.  An alternative way to think of it is that
    each pixel outside the layer boundary has the same color as the
    closest pixel inside the layer boundary.

  - Loop:  Assume that the layer repeats itself in all directions, so
    that, for example, falling off the right edge of the layer takes
    you back to the left edge.

And here's a quick comparison of the three modes:

You'll find an abyss policy option in some of the filters as well, with
a similar function.  In filters, there are additional "black" and
"white" modes, which are similar to "none", but use black and white for
out-of-bounds pixels, instead of transparency.

Veeery interesting indeed Ell! And also very clear!
Do you know exactly which tools share this same option?

Your example seems to come from the whirl-pinch distortion filter but I
do not see any abyss option in the filter option dialog... even in any
other filter option dialog... am I looking in the wrong place?

PS: also I see that in the warp tool the Abyss options remains translated
in my system language (Italian) even if I set the gimp language to
English... here and there there are some other translated particulars
like 4 controls in the render->patterns->checkboard filter, tooltips,
keyboard accelerators...small bug?



Marco Ciampa

I know a joke about UDP, but you might not get it.


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