TTF(2) TTF(2)
NAME
ttfopen, ttfscale, ttfclose, ttffindchar, ttfenumchar,
ttfgetglyph, ttfputglyph, ttfgetcontour, ttfrender,
ttfrunerender, ttfnewbitmap, ttffreebitmap, ttfblit -
TrueType renderer
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <bio.h>
#include <ttf.h>
struct TTBitmap {
u8int *bit;
int width, height, stride;
};
struct TTGlyph {
TTBitmap;
int xminpx, xmaxpx, yminpx, ymaxpx, advanceWidthpx;
/* + internals */
};
struct TTFont {
int ppem, ascentpx, descentpx;
/* + internals */
};
TTFont* ttfopen(char *filename, int size, int flags);
TTFont* ttfscale(TTFont *f, int size, int flags);
void ttfclose(TTFont *f);
int ttffindchar(TTFont *f, Rune r);
int ttfenumchar(TTFont *f, Rune r, Rune *rp);
TTGlyph* ttfgetglyph(TTFont *f, int glyphidx, int render);
void ttfputglyph(TTGlyph *g);
int ttfgetcontour(TTGlyph *g, int idx, float **fp, int *nfp);
TTBitmap* ttfrender(TTFont *f, char *s, char *e, int w, int h,
int flags, char **pp);
TTBitmap* ttfrunerender(TTFont *f, Rune *s, Rune *e, int w, int h,
int flags, Rune **pp);
TTBitmap* ttfnewbitmap(int w, int h);
void ttfblit(TTBitmap *dst, int dstx, int dsty, TTBitmap *src,
int srcx, int srcy, int w, int h);
void ttffreebitmap(TTBitmap *);
DESCRIPTION
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TTF(2) TTF(2)
Libttf is a parser and renderer of TrueType fonts. Given a
ttf font file it can produce the rendered versions of char-
acters at a given size.
Ttfopen opens the font at filename and initialises it for
rendering at size size (specified in pixels per em). Flags
is reserved for future use and should be zero. If rendering
at multiple sizes is desired, ttfscale reopens the font at a
different size (internally the size-independent data is
shared). TTfclose closes an opened font. Each instance of
a font created by ttfopen and ttfscale must be closed sepa-
rately.
A character in a TrueType font is called a glyph. Glyphs
are numbered starting from 0 and the glyph indices do not
need to follow any established coding scheme. Ttffindchar
finds the glyph number of a given rune (Unicode codepoint).
If the character does not exist in the font, zero is
returned. Note that, in TrueType fonts, glyph 0 convention-
ally contains the "glyph not found" character. Ttfenumchar
is like ttffindchar but will continue searching if the char-
acter is not in the font, returning the rune number for
which it found a glyph in *rp. It returns character in
ascending Unicode order and it can be used to enumerate the
characters in a font. Zero is returned if there are no fur-
ther characters.
Ttfgetglyph interprets the actual data for a glyph specified
by its index glyphidx. With render set to zero, the data is
left uninterpreted; currently its only use is ttfgetcontour.
With render set to one, the glyph is also rendered, i.e. a
pixel representation is produced and stored in the TTBitmap
embedded in the TTGlyph structure it returns. Although
TrueType uses a right handed coordinate system (y increases
going up), the bitmap data returns follows Plan 9 conven-
tions (and is compatible with the draw(3) mask argument).
The bottom left hand corner is at position (xmin, ymin) in
the TrueType coordinate system. Ttfputglyph should be used
to return TTGlyph structures for cleanup.
Ttfgetcontour can be used to obtain raw contour data for a
glyph. Given an index i it returns the corresponding con-
tour (counting from zero), storing a pointer to a list of
(x, y) pairs in *fp. The array is allocated with malloc(2).
The (always odd) number of points is stored in *np. The
contours correspond to closed quadratic Bézier curves and
the points with odd indices are the control points. For an
invalid index, zero is returned and *fp and *np are not
accessed. For a valid index, the number returned is the
number of contours with index ≥ i.
Ttfrender and ttfrunerender typeset a string of text
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TTF(2) TTF(2)
(specified as UTF-8 or raw Unicode, respectively) and return
a bitmap of size w and h. It attempts to typeset text start-
ing from s and up to and not including e. If e is nil, text
is typeset until a null byte is encountered. Flags speci-
fies the alignment. TTFLALIGN, TTFRALIGN and TTFCENTER
specify left-aligned, right-aligned and centered text,
respectively. TTFJUSTIFY can be or'ed with these three
options to produce text where any ``wrapped'' line is justi-
fied.
For reasons of efficiency and simplicity, libttf includes
its own format for 1 bpp bitmaps. In these bitmaps, 0 cor-
responds to transparent and 1 corresponds to opaque. Other-
wise, the format is identical to k1 image(6) bitmaps.
Ttfnewbitmap and ttffreebitmap allocate and deallocate such
bitmaps, respectively. TTGlyph structures can be used in
place of bitmaps but must be deallocated with ttfputglyph,
not ttffreebitmap. Ttfblit copies part of one bitmap onto
another. Note that bits are or'ed together -- blitting a
transparent over an opaque pixel does not produce an trans-
parent pixel.
SOURCE
/sys/src/libttf
SEE ALSO
Apple, ``TrueType™ Reference Manual''.
Microsoft, ``OpenType® specification''.
FreeType, source code (the only accurate source).
ttfrender(1).
DIAGNOSTICS
Following standard conventions, routines returning pointers
return nil on error and return an error message in errstr.
BUGS
Both ``standards'' are packages of contradictions and lies.
Apple Advanced Typography and Microsoft OpenType extensions
are not supported; similarly non-TrueType (Postscript, Bit-
map) fonts packaged as .ttf files are not supported.
The library is immature and interfaces are virtually guaran-
teed to change.
Fonts packaged as .ttc files are not supported.
HISTORY
Libttf first appeared in 9front in June, 2018.
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