Older blog entries for haruspex (starting at number 113)

26 Sep 2004 (updated 26 Sep 2004 at 02:07 UTC) »
raph, thanks for the informative post. I think I'll have to read it twice and follow the links.

the perturbation of the middle knot damps out very quickly as you traverse (S-shaped) Cornu spiral segments, but doesn't damp out at all with the circular arcs
IKARUS' circle fitting method is actually well damped, and behaves much more like the second example (as does METAFONT's IIRC).

I'm willing to tolerate a significantly larger number of primitives in this internal representation than either input through the UI or exported into a font file format after all manipulations have been done
Doesn't this have some major implications for hinting? I get the impression from FontFocus that stroke-oriented hinting is still a favoured approach.

I keep mentioning IKARUS because for many years it was the gold standard for these purposes... it's interesting you mention auto-tracing. URW produced a rather nice companion program which traced bitmaps into IK format, called LINUS. I still have a copy of the Mac version.

24 Sep 2004 (updated 24 Sep 2004 at 05:15 UTC) »
elanthis: Point taken. The battle for freedom doesn't put me in a joking mood. I'll celebrate when the likes of $CO and M$ are properly buried with a silver stake perforating their carcasses in the necessary manner.

(Yeah, I know, the stake doesn't have to be silver. But you can't be too careful. And it's 1.17am.)

23 Sep 2004 (updated 23 Sep 2004 at 17:50 UTC) »
yeupou: I agree. Could GPL-hate be self-hate?
22 Sep 2004 (updated 9 Oct 2004 at 16:48 UTC) »
Cubic Beziers are actually pretty good at making an S curve, in my opinion. Certainly, it's not uncommon in professional fonts to see a single Bezier traverse from a vertical tangent in the upper left corner to another vertical tangent in the lower right.

I agree Beziers are efficient, but I don't think this should seduce us into concluding they are natural.

If you draw the main slope of the S with, say, eight arcs, then the centers should describe a fairly continuous path in and of themselves. ... But if you don't do a good job visualizing the radii of curvature, and put the tool in novice hands, my guess is that you'll see bad curves.

That's a good point. But rather than having the user think about the circles, I wonder if they could use the abstraction of a digital spline and ducks (the non-mathematical meaning of spline). I suspect this is what Dr Karow had in mind when he came up with IKARUS' curve model.

it's probably not anywhere nearly as painful as you might think to work directly in the space of the Cornu parameters
That sounds interesting.

having an uneven baseline or x-height line is a pretty serious artifact
Surely only subpixel placement can help with non-integral lineskips? But it seems to me that (at a cost of performance, i.e. glyph caching), FontFocus could be adapted to subpixel positioning? (In the vertical, to solve the baseline problem.)

The CoolType samples in your paper do not work. In my opinion the subpixel rendering on OS X and XP (and Adobe Reader 6) does a fine job; the screen dump can only work in exceedingly rare circumstances (1:1, digital LCD of correct triplet ordering, etc) and should be deleted from the paper as a misleading comparison.

19 Sep 2004 (updated 19 Sep 2004 at 15:39 UTC) »
she said windows, not Microsoft Windows. Well, as I understand it, the company does not own the word windows, but the trade mark Microsoft Windows.
You missed Michael's point. Regardless of what M$ "owns", in common usage, the word "windows" has gained another (less useful) meaning. In real life this overloading easily results in the kind of ambiguity that his anecdote illustrated.
19 Sep 2004 (updated 19 Sep 2004 at 03:34 UTC) »
AlanHorkan, you might enjoy this great tune from Monty Python's irrepressible Eric Idle.
16 Sep 2004 (updated 16 Sep 2004 at 23:32 UTC) »
<small>people who succumb to the threat of the Ivan hurricane and run away are sending the wrong signal to Ivan. We must stand strong in the face of Ivan. We must not allow Ivan to disrupt our way of life and attack our cherished institutions. </small>
Hilarious, thanks :)

PS. Advogato, why can't me have <small>? (Thanks for allowing <cite>)

15 Sep 2004 (updated 15 Sep 2004 at 04:51 UTC) »
raph, circle segments are indeed the primitive used by IKARUS, as I've mentioned here before. This is clear from the exposition in Dr Karow's book (op cit.) and the source code therein. Also, I relate them to METAFONT deliberately, as this was explicitly the ideal around which Hobby's Bezier generation was designed. Again, this is derived from the technical descriptions given in The METAFONTbook. Of course, I know METAFONT's underlying representation and rendering engine works with Beziers, but concerning the higher level user abstraction, I stand by what I have asserted. I understand where Hobby departs from pure circles. In fact METAFONT's overall approach seems to solve most of the difficulty.

circular arcs do not have this property. You need quite a few of them to closely fit an ellipse, say.
Yes, I agree with what you write here, but I am not sure it matters. The fact is, any geometrical figure - ellipse, circle, parabola - is irrelevant to the problem of fitting a natural, drawn curve. Pure geometric shapes (with the exception of straight lines) rarely occur in a letter outline, so I disregard them as modelling test cases. Instead, I ask, how well can this primitive deal with a pre-mathematical, natural curve, as might have come from the designer's hand? How awkward is the translation? (Your curve continuity arguments are relevant theoretical ammunition here I think, although my assessments are usually subjective, not objective.)

My counter-assertion would be, for a natural curve, Beziers are not necessarily better than circle segments and further that counting control points does not prove this either way. My gut tells me that Beziers are excellent for rendering purposes but horrible for curve modelling. I certainly see advantages for Cornu over both these representations, and you've given some interesting reasons.

I have studied many IKARUS markups and not found them excessively overspecified. (It would be nice to hear from an IKARUS veteran on this.) One very intriguing thing about IKARUS is that most markups I've seen were made by non-technical draughtsmen, usually type designers themselves - Zapf, Frutiger, Spiekermann. Whereas no-one can do good Bezier drawings without a lot of training - and such drudgery would waste the time of a designer of this calibre. It took me a few years to learn how to "trick" Beziers into looking natural - and it's always a compromise.

In sum, my subjective assessments generally lead me to feel that IKARUS splines - or let's say, a mechanical spline and ducks - are quite natural to the draftsman and designer; and Beziers could not be more artificial and difficult.

We are coming at this from different angles, however. You're the mathematician, and I am just a typographer who isn't happy with the compromises that plague digital type.

13 Sep 2004 (updated 14 Sep 2004 at 01:42 UTC) »
I've also been playing with the Cornu spline...as a primitive for curve design, and am now absolutely convinced that it's better than Bezier curves.
I think it's long been clear that Beziers are not a good user abstraction for curve editing - but what's wrong with circle segments between on-curve knots, as chosen by IKARUS, METAFONT, et al? I am not sure anything could be more natural. I suppose the Cornu could be seen as a French-curve style extension of circles. I think I need to write that experimental path editor I always planned, to play with these alternatives :)

My hot metal friend Nick Summers is not out of the game. He wrote me recently with very exciting news:

I should finally be printing - letterpress, of course - by the end of this month ... I hope to be assembling the fabled Benton Engraving Machine some time soon as well. And restoring my Linotype. And casting on the Monotypes...
5 Sep 2004 (updated 5 Sep 2004 at 06:08 UTC) »
nymia: I wrote a Photoshop plugin that's downloaded 100 times a day. It's free. If I had put even a very modest sticker price on it, I'd be lucky to get one download a day. I decided that a comparatively large benefit to "the all" was preferable to a small benefit to me.

(update) nymia: The benefit I receive is the traffic. There are a couple of commercial and donation-ware plugins available from the same page, which should account for a small trickle of compensation flowing back from the free-loaders? It will never pay my mortgage, but it is -something-. After all, I only wrote the software once, if I get paid 100,000 times that might not be ethical. I don't want the bad Karma of uber-thief Gates and his kind.

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