Regarding the serialization of Spiro control points
by Fred Brennan
Greetings,
I write from the FontForge project. Of particular interest to me is the Spiro
spline feature, which was originated around ten years ago by Raph Levien.
One thing I'd like to add, (which would benefit both our projects,) is the
ability of FontForge to understand the Inkscape Spiro serialization format.
However, there are several things about the format which to me as an outsider
appear to be defects serious enough that I have no idea how to even *import*
these splines correctly, much less export our Spiro splines to this format. I
would very much like to support the _de facto_ standard Inkscape has
originated of supporting Spiro in SVG, but I am lost.
George Williams, FontForge's original author, noticed this defect over eleven
years ago.[1] Things are virtually unchanged since then, I checked `git
blame`.
Spiro has five point types, not including beginning and ending points. They
are:
* G4 curve (o)
* G2 curve (c)
* Corner (v)
* Left Constraint ([)
* Right Constraint (])
The ASCII single letters are the normal method of Spiro serialization, as
championed by Raph Levien and by us in FontForge.
Inkscape seems to create what I will call a "pseudo-SVG path". So, it is not
really an SVG path, but rather is an SVG path which undergoes transformation
into the typical Spiro format. Inkscape stores this in the "original-d"
attribute.
So, given a Bezier spline with control points defined as (x, y, c1, c2),
Inkscape interprets a control point with only (x, y) to be a corner, meanwhile
a control point with all four is a G4 curve, and (x, y, c1, NULL) is a left
constraint while (x, y, NULL, c2) is a right constraint.
I can probably overcome this, although George Williams was right to be
skeptical of this format. There is no way I can see to define a G2 curve in
this strange "original-d" format.
Thus, this email. I write to ask a few things. I suppose first of all, what
are the chances that we can convince you guys to store Spiro splines in
plate[2] format, or another widely accepted Spiro serialization format?
Second, if we cannot convince you to do that, how do I export FontForge spiros
which contain G2 control points to Inkscape's original-d format? It's not
possible, yes? So should I just silently fail and save them as G4? The curves
will not be the same if I do that. Should I disallow export to SVG w/Spiro if
glyph contains G2 control point? That seems a steep cost that will just
confuse my users, so perhaps I should abandon the whole thing if it comes to
that.
Cordial regards,
Fredrick Brennan (@ctrlcctrlv)
[1]: https://narkive.com/63FADpG3.4
[2]: https://levien.com/garden/ppedit/README, section "Plate files"
11 months, 3 weeks
BUG: Newer inkscape series crashes computer in heavy documents.
by xadaux daux
Hello,
I'm currently working on a heavy .SVG document about almost 91 layers
containing linked .PNG files in high resolution (300 dpi).
While previous series (0.91) saved successfully individual layers as single
.PDF-per-layer the latest 1.1 stands working when exporting pages and then
crashes the whole computer after 20-30 seconds. Is not posible to kill the
process manually by console.
Just want to notify devels about this particular issue.
Thank you,
Xadaux
1 year, 5 months
