Ah I was referring to the drawing with a pen process. That's was very
helpful.
I'm also impressed by the fact that the anti aliasing looks very good. I
assume this is handled by gnome and the fact that the line segment is so
small? (0.3px?)
Furthermore is pressure sensitivity data recorded per line segment?
Thanks,
Shuhao
Sent from my phone.
On Oct 1, 2014 2:43 AM, "Denis Auroux" <aur...@math.berkeley.edu> wrote:
> I'm not sure what you mean exactly by "line drawing algorithm". Do you
> mean just the process of drawing with the pen?
>
> If so: position data is received from the stylus or other input devices;
> if there hasn't been enough motion since the last
> point (by default 0.3 pixel) we discard the information and wait for
> more motion; then we draw a line segment from the
> previous point to the new one, with the given width (that of the pen in
> general, except if you have pressure sensitivity
> on your tablet and that option is enabled, then it's the pressure
> reported by the stylus times the pen width).
>
> The actual drawing of line segments is done by inserting GnomeCanvasLine
> objects into the GnomeCanvas that represents the
> document on screen. libgnomecanvas then takes care of the actual
> drawing, or rather it calls the libart_lgpl library which
> does the actual drawing.
>
> If you mean the shape recognizer detection of lines, it's a different
> story. We treat the stroke as a piece of wire and
> calculate its center of mass (x_0,y_0) and its inertia matrix (integrals
> of (x-x_0)^2, (x-x_0)(y-y_0), and (y-y_0)^2 along
> the wire). If the suitably normalized inertia matrix has small enough
> determinant then the wire is "long and thin" and we
> declare it to be a line.
>
> Denis
>
>
> On 10/01/2014 05:24 AM, Shuhao wrote:
> > Hey,
> >
> > I'm curious to how the xournal line drawing algorithm works. Is there a
> > document somewhere documenting its process? This algorithm is the best
> > I've seen from a couple of programs and I'm wondering how exactly it's
> > accomplished. Unfortunately my C skills are not as good and somewhat
> > rusty so I'm having some trouble reading through the xo-paint file.
> >
> > Thanks,
> > Shuhao
> >
> >
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> --
> Denis Auroux
> UC Berkeley, Department of Mathematics aur...@math.berkeley.edu
> Institut Henri Poincare, Paris aur...@ihp.fr
>
>
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