Re: [ft] Using SVG Font Glyph Data In FreeType

[Andy Kellett]

Hi,

Yes, you described it quite accurately :) While I can do the SVG path 
conversions/handling myself, the real problem (and while it probbably 
wasnt described as clearly myself) is telling freetype how to handle the 
curves etc. that I am reading frm the SVG.

I have already loaded, parsed and broken down the SVG path data into 
sections, rendering the article with placeholders etc. An example of 
some of the SVG font data (using standard path commands) is:

<glyph unicode="s" horiz-adv-x="556"
d="M511,197C511,424,207,412,207,549C207,599,236,626,285,626C346,626,355,571,355,517L502,517C512,668,439,734,292,734C108,734,54,644,54,531C54,316,358,308,358,178C358,129,333,96,282,96C199,96,196,154,196,223L45,223C37,98,72,-12,259,-12C374,-12,511,10,511,197 
Z" />
<glyph unicode="&#8220;" horiz-adv-x="444"
d="M395,722L299,722L226,525L360,525L395,722M217,722L121,722L48,525L182,525L217,722 
Z" />
<glyph unicode="&#8221;" horiz-adv-x="444"
d="M48,525L144,525L217,722L83,722L48,525M226,525L322,525L395,722L261,722L226,525 
Z" />
<glyph unicode="&#8250;" horiz-adv-x="222"
d="M124,464L9,464L95,267L7,75L123,75L215,267L124,464 Z" />

The struct I found in the documentation seemed to be the way to go to 
instruct how to tell FreeType what to do with a curve, what to do with a 
bezier, as all the examples assume that you have a 2d array of 
coordinates, and a simple square-like object.

The glyph data originates from a tool the guys use to construct an 
article/catalogue layout, which is then exported as an SVG file and 
distributed with the app. Because they use many different styles, fonts, 
types and shapes, the SVG contains the multiple fonts used and puts the 
glyphs of the used characters from that font into it, including the 
custom shapes they use for different symbols. Once these are out there, 
its much easier to update the SVG files than to redistribute a download 
to thousands of customers just to add a font.

Id rather have freetype handle the fonts rather than manually making a 
bitmap, and then scaling/resizing the image with a traditional image 
scale (which looks crappy). It would also be much quicker.

Are there any examples to manually building a glyph/character that 
consists of curves, straights and filled and so forth? If I knew the 
syntax for how to construct a mixed array of coordinate types to do 
this, then writing the SVG conversion would be trivial. I had just 
assumed that people used SVG fonts in freetype commonly, as most of the 
big libraries do it. Thanks.

Kind Regards,

Andy 'FishGuy876' Kellett
FishGuy876 of Brainstorm < http://brainstorm.untergrund.net >
--

Email: address@hidden
ICQ: 9701389 AOL: FishGuy876 Yahoo: FishGuy876
URL: http://www.cvgm.net - Old/Newskool Computer Music

On 4/8/2010 8:08 AM, Michiel Kamermans wrote:
> Hi Tom, Werner, Andy,
>
> > If you're looking for sample code that reads SVG, I don't think that's
> > something FreeType does. The FreeType side is relatively easy, and
> > Werner has shown you sample code for that. The SVG side is not
> > trivial; it requires XML parsing and should probably be done with a
> > library for SVG (but I don't know what library to recommend).
>
> Depending on how he built his SVG, this should essentially be trivial.
> As long as his SVG consists of paths rather than predefined shapes like
> rectangles and circles (which, given glyph outlines, I wouldn't think he
> uses), these elements have the wonderfully names "d" attribute, which
> contains a normal human readable string of path construction
> instructions. For instance:
>
> <path d="M 10 10 L 30 20 Q 20 40 50 50"/>
>
> In this string, "M" signifies "move to .../...", "L" is "line to
> .../...", and "Q" is "quadratic bezier curve over .../... to .../..."
> (there's also "C" for cubic bezier, and there may be a "Z" at the end of
> the string to signify 'close this path by doing a lineto back to the
> original starting point').
>
> These string segments should be almost trivially simple to map to
> FreeType, since the basic instructions are the same for pretty much all
> things related to fonts: move, line, curve (if you're lucky, 2nd and 3rd
> order, if not, it's just 3rd order with a need to model 2nd order curves
> as 3rd order).
>
> If I understand Andy correctly, he'd like to map these primitive outline
> commands to the corresponding FreeType rules (the FT_outline_Functs
> structures) and then hand off the set of rules for FreeType to work its
> magic on. I've had a look at
> http://freetype.sourceforge.net/freetype2/docs/tutorial/example3.cpp but
> it seems incomplete for the purpose of what he wants to do, as it seems
> to demonstrate how to deal with a purely line data shape, rather than
> one consisting of curve data. The shape as used in the example code uses
> only on-curve vectors, rather than structs that allow specification of
> on-curve coordinates, and off-curve bezier control points.
>
> Andy, if I might ask, where did you get your glyph SVG data from in the
> first place? Are you extracting them from fonts, or are these vector
> outlines made in (for instance) Inkscape that you want to pass to
> FreeType for text rendering?
>
> If the first, is there a reason for not simply using the fonts you
> extracted the glyphs from? If the latter, would it not make more sense
> to do your outline definition in something like FontForge instead, and
> build an actual font that FreeType can use? Of course, option number
> three is you're doing dynamic glyph definitions, using them in
> dynamically generated images with text... but in that case it might be
> far more sensible to build the entire graphic as an SVG image instead.
>
> - Mike "Pomax" Kamermans
> nihongoresources.com
>
>
>
>
>
>
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