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Re: [Devel] Rendering (by FreeType) and hinting of Latin small 'a'
From: |
Vadim Plessky |
Subject: |
Re: [Devel] Rendering (by FreeType) and hinting of Latin small 'a' |
Date: |
Wed, 11 Sep 2002 12:15:40 +0400 |
User-agent: |
KMail/1.4.6 |
Hello David!
On Tuesday 10 September 2002 12:43 am, David Turner wrote:
| Hello Vadim,
|
| Vadim Plessky wrote:
| > I'd like to discuss (again) rendering of Serif fonts, and, in particular
| > (to narrow the scope) - Latin small 'a'.
| > I have prepared a web page with examples demonstrating different
| > rendering of this glyph
| > http://freetype.newmail.ru/misc/hinting-a.html
| >
| > [...]
| >
| > Now about problem I see at a moment.
| > 1) topology of 'a' is destroyed at all examples, except non-AA
| > rendering. I refer here to central, near-horizontal curve, in the middle
| > of 'a' enabling sub-pixel rgb decimation doesn't help here.
|
| I have introduced some changes in the automatic and Postscript hinters
| lately to deal with disappearing curved diagonals (like in "S" or "2").
| There are chances that these might also enhance the hinting of
| your "a"s. Could you test the rendering of the current CVS code
| to see if something changed ??
I upgraded to FT 2.13-RC1 (Aug.28 snapshot), and indeed that problem was
fixed.
But new ones appeared. :-(
|
| > 2) in ftview rendering, even bottom part of 'a' is disconnected from the
| > vertical stem.
| > It's very visible at screenshot in natural size, and on enlarged s/s as
| > well.
|
| This is not very surprising, since the second glyph doesn't have any
| hint on the lower stem. The Postscript hinter relies on what is provided
| by the font file and won't try to detect stems on its own.
That was intentional. And FT 2.13, BTW, renders all 3 glyphs identically!
So it seems it auto-aligns bottom part of the 'a'.
|
| Note that the auto-hinter does render all three glyphs identically, since
| their outlines are the same.
|
| > 3) My testing of 5 different Times clones (variants), in addition to the
| > version I develop, demonstrates, that all variants of Times, with
| > exception of Times New Roman, have similiar problem described above.
| > See screenshots at th ebottom of th epage (Times New Roman is 2nd in
| > series, each three rendered glyphs are 12pt, 11pt, 10pt Latin 'a')
| >
| > Here are my questions:
| > a) can this *topology* (visually broken curve) issue be fixed?
| > I demonstrated problem on example of 'a', but many other glyphs are
| > affected (in AA or RGN-AA modes), too.
|
| Maybe, please test and report your opinion on that..
ok, I created new page dedicated to this problem, together with new test font
(experimental-a, atatched, there is a link to it from the page as well)
Please check it out:
http://freetype.newmail.ru/misc/experimental-a.html
I know that from some countries (Australia? Ireland?) that location can be
slow to access, so if you have timeout on server - please e-mail me, I can
send files as mail attachment.
BTW: handling of Topology is much better in FT 2.1.3 than in FT 2.0.9
But still FT can generate, on occasion, broken contours...
Comments from my page (FT 2.1.3-RC1 rendering, AA enabled):
"All glyphs are rendered blurred. Compare this to rendering on screenshot
below, which uses auto-hinter (where text is crisp). My understanding is that
PS gray renderer uses different path/code when it renders glyphs with hints
generated by auto-hinter (in contrast with PS glyphs which have pre-defined
PS hints). This is very strange and undesirable. I consider this is a bug in
FreeType 2.1.3-RC1 "
|
| > b) how rendering (by FreeType, not too much interested in Adobe Type
| > Manager or Windpows' rasterizer) of middle part of 'a' can be enhanced?
| > Should I artificially deformate curve to make constrains snapping to
| > horizontal position? (like is done in Times New Roman)
| > This is not very desirable, as 'a' in Times New Roman has too small
| > bottom part, IMO, and this is not easy for screen reading.
| > Diagonal hinting also doesn't help here, as, frankly speaking, this part
| > does't conform to diagonal hinting definition.
|
| Try to make the stem slightly larger when it connects to the vertical
| stem in the "a". This should help make it stronger/visible. Otherwise,
| I don't see what could really done..
Ok, please look at URL above.
I did it slightly larger, but this doesn't help.
variant of 'a' at f, g,h positions in font demonstrate *what* can be done, and
confirm my statement that FT *can* handle such cases.
Hope my experimental font will help to make rendering better.
|
| > c) Is it possible, in some way, to increase *tension* for FT rasterizer
| > when it follows some part of the contour/curve?
| > It's like of driving a car with high speed, and follow smooth turn to,
| > say, left at 80km/hour.
| > It can be done, if you increase your speed instantly /with acceleration/
| > :-) So, I think we should find a way to do the same with such curves. Is
| > it possible to do? What are your opinions?
|
| I fail to understand precisely what you mean here. Do you have anything
| more visual as an explanation (maybe a small graphics could help ??)
variuant under 'b' position demonstrates that this (for some reason) doesn't
help.
I moved control points by 100 units far away from position they were before,
it's like increasing acceleration when driving.
I will try to experiment more and will let you know wether I achieved
something.
My next standpoint is 'a' from Garamond and Caslon - they always had much more
problems (in rendering) than *trivial Times* :-)
|
| Best Regards,
|
| - David
| _______________________________________________
| Devel mailing list
| address@hidden
| http://www.freetype.org/mailman/listinfo/devel
My best regards,
--
Vadim Plessky
http://kde2.newmail.ru (English)
33 Window Decorations and 6 Widget Styles for KDE
http://kde2.newmail.ru/kde_themes.html
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http://kde2.newmail.ru/themes/
experimental-a-font.zip
Description: Zip archive
- [Devel] Rendering (by FreeType) and hinting of Latin small 'a', Vadim Plessky, 2002/09/03
- [Devel] freetype on cygwin., George Williams, 2002/09/09
- Re: [Devel] Rendering (by FreeType) and hinting of Latin small 'a', David Turner, 2002/09/09
- Re: [Devel] Rendering (by FreeType) and hinting of Latin small 'a',
Vadim Plessky <=
- [Devel] 'tension' in splines, Hermite Splines [Re: Rendering (by FreeType) and hinting of Latin small 'a'], Vadim Plessky, 2002/09/11
- RE: [Devel] 'tension' in splines, Hermite Splines [Re: Rendering (by FreeType) and hinting of Latin small 'a'], Graham Asher, 2002/09/11
- Re: [Devel] 'tension' in splines, Hermite Splines [Re: Rendering (by FreeType) and hinting of Latin small 'a'], David Turner, 2002/09/11
- Re: [Devel] 'tension' in splines, Hermite Splines [Re: Rendering (by FreeType) and hinting of Latin small 'a'], Vadim Plessky, 2002/09/12
- Re: [Devel] 'tension' in splines, Hermite Splines [Re: Rendering (by FreeType) and hinting of Latin small 'a'], George Williams, 2002/09/12
- Re: [Devel] 'tension' in splines, Hermite Splines [Re: Rendering (by FreeType) and hinting of Latin small 'a'], oergiR, 2002/09/12
- Re: [Devel] 'tension' in splines, Hermite Splines [Re: Rendering (by FreeType) and hinting of Latin small 'a'], Vadim Plessky, 2002/09/12
- Re: [Devel] 'tension' in splines, Hermite Splines [Re: Rendering (by FreeType) and hinting of Latin small 'a'], Rogier van Dalen, 2002/09/13
- Re: [Devel] 'tension' in splines, Hermite Splines [Re: Rendering (by FreeType) and hinting of Latin small 'a'], Just van Rossum, 2002/09/13