Re: [Devel] 'tension' in splines, Hermite Splines [Re: Rendering (by FreeType) and hinting of Latin small 'a']

[Vadim Plessky]

Hello Rogier!

On Thursday 12 September 2002 3:33 pm, oergiR wrote:
|  Hello Vadim,
|
|  Just a reaction to the TrueType bits...
|
|  > Well, I have checked today, with help of TtfMod, complexity of so-called
|  > "well-hinted TrueType fonts". In particular, Times New Roman TTF.
|  > And I can tell you that level of complexity I found, far exceeded my
|  > expectations!
|  > Here are some numbers illustrating TNR complexity.
|  > Number is number of instructions, to be precise: instructions+operands,
|  > executed by interpreter.
|  > And this doesn't include calls to subroutines!
|  >
|  >   capital small
|  > A 427 596
|  > (...)
|  >
|  > Returning to samll Latin 'a' - it required 596 bytes (opcode+operands)
|  > for *right* hinting and good rendering.
|
|  This is opcodes+operands as you say. The actual number of instructions
|  executed for "a" is 236 (including function calls), and something around
| 425 for nonsquare pixels. I believe these figures are mostly due to the

Yes, seems like that.
As there is no TT-opcodes -> TT assembler converter (disassembler), and no 
assembler (TT asembler -> TT-Opcodes) I am aware off, I used exactly amount 
of bytes per glyph.
Anyway, I was interested in *estimation*, not in precise figure.

| large amounts of delta hints, which are almost never needed when using an
| anti-aliased rasteriser, in my experience.
|
|  Georgia, which is hinted far better than TNR, if you ask me, executes only
|  99 to 103 instructions for "a".

I like how you pronounce word "only" ;-)

|
|  > Depending on outline quality and origin (TTF or PS Type1), FontLab's
|  > auto-hinter produced from 7 to 15 *high-level* TrueType hints.
|  > I name them high-level, as NimbusRoman and NimbusSans TTF's have 196 and
|  170
|  > operations(addresses) for 'a'. At least that's what TtfMod tells me.
|  > So it seems FontLab translates those *high-level* TrueType hints into
|  > low-level TT opcodes, complements them with stack data, etc.
|  >
|  > My point is that 15 operations per glyph are *reasonable*, and can be
|  > overviewed/hinted by a man (as you can see from URL above, TT
|  > auto-hinter results in FL4 are acceptable in mnay cases, but need
|  > correction by hand) 196 operations, not speaking about 600, can't be
|  > coded by a man.
|
|  As you say, the number of "operations" is the important thing. I am right
|  now working on a compiler which takes something looking like C and
| produces TT instructions. Without delta hints, I use about 20 to 40 lines
| per glyph, which compile to about 10 times those amount of bytes in the
| instructions. IMO, a few thousand lines per font can be coded.

Ah, cool!
When do you plan to release first Beta?

|
|  > (....)
|  > Problem is that TrueType outlines have *too many* points, and this
|  *decreases*
|  > font quality in most cases.
|
|  This is true, also because of the conversion from Bezier splines. I'm not
|  sure, however, this actually causes a lower font quality.

Well, you will notice difference on professional typesetting machine 
(2500dpi), I guess.
I also found printouts in Times New Roman difficult to read, as its outlines 
very artificially distorted to achieve best rendering results on screen.

|
|  > (....)
|
|  Bye,
|
|  Rogier
|  _______________________________________________
|  Devel mailing list
|  address@hidden
|  http://www.freetype.org/mailman/listinfo/devel

Cheers,
-- 

Vadim Plessky
http://kde2.newmail.ru  (English)
33 Window Decorations and 6 Widget Styles for KDE
http://kde2.newmail.ru/kde_themes.html
KDE mini-Themes
http://kde2.newmail.ru/themes/