Glyphs is a pure-tcl library for digging into TrueType font-files.
Glyphs is able to extract the vectorial paths of each glyph - points, lines, curves.
This is our first quick trip; just open a .ttf, look inside and close
> package require glyphs > set fObj [glyphs open "arial.ttf"] > set ng [$fObj get numGlyphs] > puts "found $ng glyphs" > $fObj close
Reopen the .ttf file
> set fObj [glyphs open "arial.ttf"]
we already know how to get the number-of-glyphs
> set res1 [$fObj get numGlyphs] 1674
and we can also get the overall-bounding box, or where the descender-line is placed
> set res2 [$fObj get bbox] -1361 -665 4096 2060 >set res3 [$fObj get Descender] -434
but there're a lot of properties and the better way to know which properties are set is:
> set props [$fObj get] fontPath numGlyphs bbox unitsPerEm fontRevision Ascender Descender .....
WARNING: many properties may be added/removed for "glyphs 1.0"
The quickest way to locate a single glyph is through its glyph-index. You know that "arial.ttf" has 1674 glyphs, therefore you can get all glyphs from 0 to 1674.
now let' take the 144th glyph set g144 $fObj glyph 144 As with fObj's properties, we can get some specific glyph's property: $g144 get index ;# --> 144 $g144 get bbox ;# --> 1 0 1936 1466 Forget about the "instructions" property it' a binary string "glyphs" is not currently able to decode. (Probably it will removed in the next revision) The most important properties are "points" and "commandpaths" Let's take a glyph simpler than 144 set g103 $fObj glyph 103 set L $g103 get points
{99 714 1 99 1079 0 ...} {299 711 1 299 446 0 ...} {516 1556 1 516 1761 1 ...} {889 1556 1 ...} Result looks like a list of 4 lists (4 contours). Each contour is made of a sequence of triples x y flag. Flag "1" means that point (x,y) is on-curve, Flag "0" means point (x,y) is the control point of a Quadratic Bezier curve.
But, how to translate these "points" in a parametric curve ?
set L $g103 get commandpaths
{{MOVETO 99 714} {QUADTO 99 1079 295.0 1285.5} ...} {{MOVETO 299 711} {QUADTO 299 446 441.5 293.5} ... } {{MOVETO 516 1556} {LINETO 516 1761} ... } {{MOVETO 889 1556} {LINETO 889 1761} ...} Result is a list of (4) contours. Each contour is made of a sequence of simple abstract commands:
MOVETO x y -- set (x,y) as the current point LINETO x y -- draw a line from current point to (x,y). (x,y) then becomes the current point QUADTO x1 y1 x2 xy -- draw a quadratic bezier from current point, to (x1,y1) (control point) and to (x2,y2) (end-point) (x,y) then becomes the current point
It's your app's responsability to translate these 'abstract commands' in real commands. A naive implementation for the canvas widget could be:
proc CommandPaths2Canvas { cvs paths } {
foreach path $paths {
# first command should be MOVETO
foreach pCmd $path {
set points [lassign $pCmd cmd]
switch -- $cmd {
MOVETO {
;
}
LINETO {
$cvs create line $lastX $lastY {*}$points
}
QUADTO {
$cvs create line $lastX $lastY {*}$points -smooth true
}
default { error "unrecognized path command \"$cmd\"" }
}
set lastX [lindex $points end-1]
set lastY [lindex $points end]
}
}}
There's no much more to do with a single-glyph. Since it's a dynamic object, you can free space when it's no more useful
$g133 close
but, you are not required to do it. In fact, when the 'font-file' is closed
$fObj close #; -- THIS frees space also for all the extracted glyphs
all space is freed.
* More on accessing glyphs *
We've seen the standard way to access a glyph by-index. The major part of TTF holds a table for converting "character" (unicode) to index.
$fObj unicode2glyphIndex "A" $fObj unicode2glyphIndex "ß" ; # unicode char \u03B2 (greek letter "Beta") $fObj unicode2glyphIndex \u03B2 ; # unicode char \u03B2 (greek letter "Beta") $fObj numcode2glyphIndex 946 ; # it's always the greek letter "Beta" !
For your convenience, you can access a glyph, with two new methods
$fObj glyphByUnicode "ß" ; # glyph by Unicode $fObj glyphByCharCode 946 ; # glyph by CharCode