Edit > Stroke Selection, Line width odd/even and antialiasing

Hi Gimp-user,

Just wondering why, odd pixel widths look different than even pixel
widths when using Edit > Stroke Selection?

The odd pixel lines looked aliased, while the even pixel lines don't
(only their corners).

When drawing icons and shapes, do you make a conscious decision to stroke
the line with an odd or even line width?

I tested this by drawing a selection on a layer and stroking it with
line width 1, then adding a layer, moving the selection to the right,
and stroking it with line width 2. I repeated that 4 times increasing
the line width each time.

Thank you.

Hi,

On Mon, 2009-06-15 at 22:50 -0500, DJ wrote:

> Just wondering why, odd pixel widths look different than even pixel
> widths when using Edit > Stroke Selection?

Just think about it. You are stroking along the pixel borders. An even
line width will cover pixels exactly. An odd line width will only cover
the outer pixels by 50%.


Sven

Sven Neumann (sven@gimp.org) wrote:
> On Mon, 2009-06-15 at 22:50 -0500, DJ wrote:
> > Just wondering why, odd pixel widths look different than even pixel
> > widths when using Edit > Stroke Selection?
>
> Just think about it. You are stroking along the pixel borders. An even
> line width will cover pixels exactly. An odd line width will only cover
> the outer pixels by 50%.

Actually at some point someone seems to have done a "fix" that offsets
the stroke by 0.5 pixels if the brush has an odd width. At least it
feels like this, since stroking a 1 pixel brush with the paintbrush
yields a black one-pixel line offset 0.5 pixels against the selection
outline.

Argh.

Bye,
Simon