Imager::Font(3) User Contributed Perl Documentation Imager::Font(3)NAMEImager::Font - Font handling for Imager.
SYNOPSIS
use Imager;
$t1font = Imager::Font->new(file => 'pathtofont.pfb');
$ttfont = Imager::Font->new(file => 'pathtofont.ttf');
$w32font = Imager::Font->new(face => 'Times New Roman');
$blue = Imager::Color->new("#0000FF");
$font = Imager::Font->new(file => 'pathtofont.ttf',
color => $blue,
size => 30);
($neg_width,
$global_descent,
$pos_width,
$global_ascent,
$descent,
$ascent,
$advance_width,
$right_bearing) = $font->bounding_box(string=>"Foo");
my $bbox_object = $font->bounding_box(string=>"Foo");
# documented in Imager::Draw
$img->string(font => $font,
text => "Model-XYZ",
x => 15,
y => 40,
size => 40,
color => $red,
aa => 1);
DESCRIPTION
This module handles creating Font objects used by Imager. The module
also handles querying fonts for sizes and such. If both T1lib and
FreeType were available at the time of compilation then Imager should
be able to work with both TrueType fonts and t1 Postscript fonts. To
check if Imager is t1 or TrueType capable you can use something like
this:
use Imager;
print "Has truetype" if $Imager::formats{tt};
print "Has t1 postscript" if $Imager::formats{t1};
print "Has Win32 fonts" if $Imager::formats{w32};
print "Has Freetype2" if $Imager::formats{ft2};
new This creates a font object to pass to functions that take a font
argument.
$font = Imager::Font->new(file => 'denmark.ttf',
index => 0,
color => $blue,
size => 30,
aa => 1);
This creates a font which is the TrueType font denmark.ttf. It's
default color is $blue, default size is 30 pixels and it's rendered
anti-aliased by default. Imager can see which type of font a file
is by looking at the suffix of the file name for the font. A
suffix of "ttf" is taken to mean a TrueType font while a suffix of
"pfb" is taken to mean a Type 1 Postscript font. If Imager cannot
tell which type a font is you can tell it explicitly by using the
"type" parameter:
$t1font = Imager::Font->new(file => 'fruitcase', type => 't1');
$ttfont = Imager::Font->new(file => 'arglebarf', type => 'tt');
The "index" parameter is used to select a single face from a font
file containing more than one face, for example, from a Macintosh
font suitcase or a ".dfont" file.
If any of the "color", "size" or "aa" parameters are omitted when
calling "Imager::Font->new()" the they take the following values:
color => Imager::Color->new(255, 0, 0, 0); # this default should be changed
size => 15
aa => 0
index => 0
To use Win32 fonts supply the face name of the font:
$font = Imager::Font->new(face=>'Arial Bold Italic');
There isn't any access to other logical font attributes, but this
typically isn't necessary for Win32 TrueType fonts, since you can
construct the full name of the font as above.
Other logical font attributes may be added if there is sufficient
demand.
Parameters:
· "file" - name of the file to load the font from.
·
"face" - face name. This is used only under Win32 to create a
GDI based font. This is ignored if the "file" parameter is
supplied.
· "type" - font driver to use. Currently the permitted values
for this are:
· "tt" - FreeType 1.x driver. Supports TrueType (".ttf")
fonts.
·
"t1" - T1 Lib driver. Supports Postscript Type 1 fonts.
Allows for synthesis of underline, strikethrough and
overline.
· "ft2" - FreeType 2.x driver. Supports many different font
formats. Also supports the transform() method.
· "color" - the default color used with this font. Default: red.
· "size" - the default size used with this font. Default: 15.
· "utf8" - if non-zero then text supplied to $img->string(...)
and $font->bounding_box(...) is assumed to be UTF-8 encoded by
default.
· "align" - the default value for the $img->string(...) "align"
parameter. Default: 1.
· "vlayout" - the default value for the $img->string(...)
"vlayout" parameter. Default: 0.
· "aa" - the default value for the $im->string(...) "aa"
parameter. Default: 0.
· "index" - for font file containing multiple fonts this selects
which font to use. This is useful for Macintosh "DFON"
(.dfont) and suitcase font files.
If you want to use a suitcase font you will need to tell Imager
to use the FreeType 2.x driver by setting "type" to 'ft2':
my $font = Imager::Font->new(file=>$file, index => 1, type=>'ft2')
or die Imager->errstr;
bounding_box()
Returns the bounding box for the specified string. Example:
my ($neg_width,
$global_descent,
$pos_width,
$global_ascent,
$descent,
$ascent,
$advance_width,
$right_bearing) = $font->bounding_box(string => "A Fool");
my $bbox_object = $font->bounding_box(string => "A Fool");
$neg_width
the relative start of a the string. In some cases this can be
a negative number, in that case the first letter stretches to
the left of the starting position that is specified in the
string method of the Imager class
$global_descent
how far down the lowest letter of the entire font reaches below
the baseline (this is often j).
$pos_width
how wide the string from the starting position is. The total
width of the string is "$pos_width-$neg_width".
$descent
$ascent
the same as <$global_descent> and <$global_ascent> except that
they are only for the characters that appear in the string.
$advance_width
the distance from the start point that the next string output
should start at, this is often the same as $pos_width, but can
be different if the final character overlaps the right side of
its character cell.
$right_bearing
The distance from the right side of the final glyph to the end
of the advance width. If the final glyph overflows the advance
width this value is negative.
Obviously we can stuff all the results into an array just as well:
@metrics = $font->bounding_box(string => "testing 123");
Note that extra values may be added, so $metrics[-1] isn't
supported. It's possible to translate the output by a passing
coordinate to the bounding box method:
@metrics = $font->bounding_box(string => "testing 123", x=>45, y=>34);
This gives the bounding box as if the string had been put down at
"(x,y)" By giving bounding_box 'canon' as a true value it's
possible to measure the space needed for the string:
@metrics = $font->bounding_box(string=>"testing",size=>15,canon=>1);
This returns the same values in $metrics[0] and $metrics[1], but:
$bbox[2] - horizontal space taken by glyphs
$bbox[3] - vertical space taken by glyphs
Returns an Imager::Font::BBox object in scalar context, so you can
avoid all those confusing indexes. This has methods as named
above, with some extra convenience methods.
Parameters are:
· "string" - the string to calculate the bounding box for.
Required.
· "size" - the font size to use. Default: value set in
Imager::Font->new(), or 15.
· "sizew" - the font width to use. Default to the value of the
"size" parameter.
· "utf8" - For drivers that support it, treat the string as UTF-8
encoded. For versions of perl that support Unicode (5.6 and
later), this will be enabled automatically if the 'string'
parameter is already a UTF-8 string. See "UTF-8" for more
information. Default: the "utf8" value passed to
Imager::Font->new(...) or 0.
· "x", "y" - offsets applied to @box[0..3] to give you a adjusted
bounding box. Ignored in scalar context.
· "canon" - if non-zero and the "x", "y" parameters are not
supplied, then $pos_width and $global_ascent values will
returned as the width and height of the text instead.
string()
The $img->string(...) method is now documented in "string()" in
Imager::Draw
align(string=>$text,size=>$size,x=>...,y=>...,valign =>
...,halign=>...)
Higher level text output - outputs the text aligned as specified
around the given point (x,y).
# "Hello" centered at 100, 100 in the image.
my ($left, $top, $right, $bottom) =
$font->align(string=>"Hello",
x=>100, y=>100,
halign=>'center', valign=>'center',
image=>$image);
Takes the same parameters as $font->draw(), and the following extra
parameters:
· "valign" - Possible values are:
"top"
Point is at the top of the text.
"bottom"
Point is at the bottom of the text.
"baseline"
Point is on the baseline of the text (default.)
"center"
Point is vertically centered within the text.
· "halign"
· "left" - the point is at the left of the text.
· "start" - the point is at the start point of the text.
· "center" - the point is horizontally centered within the
text.
· "right" - the point is at the right end of the text.
· "end" - the point is at the end point of the text.
· "image" - The image to draw to. Set to "undef" to avoid
drawing but still calculate the bounding box.
Returns a list specifying the bounds of the drawn text.
dpi()
dpi(xdpi=>$xdpi, ydpi=>$ydpi)
dpi(dpi=>$dpi)
Set or retrieve the spatial resolution of the image in dots per
inch. The default is 72 dpi.
This isn't implemented for all font types yet.
Possible parameters are:
· "xdpi", "ydpi" - set the horizontal and vertical resolution in
dots per inch.
· "dpi" - set both horizontal and vertical resolution to this
value.
Returns a list containing the previous "xdpi", "ydpi" values.
transform()
$font->transform(matrix=>$matrix);
Applies a transformation to the font, where matrix is an array ref
of numbers representing a 2 x 3 matrix:
[ $matrix->[0], $matrix->[1], $matrix->[2],
$matrix->[3], $matrix->[4], $matrix->[5] ]
Not all font types support transformations, these will return
false.
It's possible that a driver will disable hinting if you use a
transformation, to prevent discontinuities in the transformations.
See the end of the test script t/t38ft2font.t for an example.
Currently only the ft2 (FreeType 2.x) driver supports the
transform() method.
See samples/slant_text.pl for a sample using this function.
Note that the transformation is done in font co-ordinates where y
increases as you move up, not image co-ordinates where y decreases
as you move up.
has_chars(string=>$text)
Checks if the characters in $text are defined by the font.
In a list context returns a list of true or false value
corresponding to the characters in $text, true if the character is
defined, false if not. In scalar context returns a string of "NUL"
or non-"NUL" characters. Supports UTF-8 where the font driver
supports UTF-8.
Not all fonts support this method (use $font->can("has_chars") to
check.)
· "string" - string of characters to check for. Required. Must
contain at least one character.
· "utf8" - For drivers that support it, treat the string as UTF-8
encoded. For versions of perl that support Unicode (5.6 and
later), this will be enabled automatically if the 'string'
parameter is already a UTF-8 string. See "UTF-8" for more
information. Default: the "utf8" value passed to
Imager::Font->new(...) or 0.
face_name()
Returns the internal name of the face. Not all font types support
this method yet.
glyph_names(string=>$string [, utf8=>$utf8 ][, reliable_only=>0 ] );
Returns a list of glyph names for each of the characters in the
string. If the character has no name then "undef" is returned for
the character.
Some font files do not include glyph names, in this case FreeType 2
will not return any names. FreeType 1 can return standard names
even if there are no glyph names in the font.
FreeType 2 has an API function that returns true only if the font
has "reliable glyph names", unfortunately this always returns false
for TrueType fonts. This can avoid the check of this API by
supplying "reliable_only" as 0. The consequences of using this on
an unknown font may be unpredictable, since the FreeType
documentation doesn't say how those name tables are unreliable, or
how FT2 handles them.
Both FreeType 1.x and 2.x allow support for glyph names to not be
included.
draw
This is used by Imager's string() method to implement drawing text.
See "string()" in Imager::Draw.
MULTIPLE MASTER FONTS
The FreeType 2 driver supports multiple master fonts:
is_mm()
Test if the font is a multiple master font.
mm_axes()
Returns a list of the axes that can be changes in the font. Each
entry is an array reference which contains:
1. Name of the axis.
2. minimum value for this axis.
3. maximum value for this axis
set_mm_coords(coords=>\@values)
Blends an interpolated design from the master fonts. @values must
contain as many values as there are axes in the font.
For example, to select the minimum value in each axis:
my @axes = $font->mm_axes;
my @coords = map $_->[1], @axes;
$font->set_mm_coords(coords=>\@coords);
It's possible other drivers will support multiple master fonts in the
future, check if your selected font object supports the is_mm() method
using the can() method.
UTF-8
There are 2 ways of rendering Unicode characters with Imager:
· For versions of perl that support it, use perl's native UTF-8
strings. This is the simplest method.
· Hand build your own UTF-8 encoded strings. Only recommended if
your version of perl has no UTF-8 support.
Imager won't construct characters for you, so if want to output Unicode
character 00C3 "LATIN CAPITAL LETTER A WITH DIAERESIS", and your font
doesn't support it, Imager will not build it from 0041 "LATIN CAPITAL
LETTER A" and 0308 "COMBINING DIAERESIS".
To check if a driver supports UTF-8 call the utf8() method:
utf8()
Return true if the font supports UTF-8.
Native UTF-8 Support
If your version of perl supports UTF-8 and the driver supports UTF-8,
just use the $im->string() method, and it should do the right thing.
Build your own
In this case you need to build your own UTF-8 encoded characters.
For example:
$x = pack("C*", 0xE2, 0x80, 0x90); # character code 0x2010 HYPHEN
You need to be be careful with versions of perl that have UTF-8
support, since your string may end up doubly UTF-8 encoded.
For example:
$x = "A\xE2\x80\x90\x41\x{2010}";
substr($x, -1, 0) = "";
# at this point $x is has the UTF-8 flag set, but has 5 characters,
# none, of which is the constructed UTF-8 character
The test script t/t38ft2font.t has a small example of this after the
comment:
# an attempt using emulation of UTF-8
DRIVER CONTROL
If you don't supply a 'type' parameter to Imager::Font->new(), but you
do supply a 'file' parameter, Imager will attempt to guess which font
driver to used based on the extension of the font file.
Since some formats can be handled by more than one driver, a priority
list is used to choose which one should be used, if a given format can
be handled by more than one driver.
priorities
The current priorities can be retrieved with:
@drivers = Imager::Font->priorities();
You can set new priorities and save the old priorities with:
@old = Imager::Font->priorities(@drivers);
If you supply driver names that are not currently supported, they
will be ignored.
Imager supports both T1Lib and FreeType 2 for working with Type 1
fonts, but currently only T1Lib does any caching, so by default
T1Lib is given a higher priority. Since Imager's FreeType 2
support can also do font transformations, you may want to give that
a higher priority:
my @old = Imager::Font->priorities(qw(tt ft2 t1));
register
Registers an extra font driver. Accepts the following parameters:
· type - a brief identifier for the font driver. You can supply
this value to "Imager::Font->new()" to create fonts of this
type. Required.
· class - the font class name. Imager will attempted to load
this module by name. Required.
· files - a regular expression to match against file names. If
supplied this must be a valid perl regular expression. If not
supplied you can only create fonts of this type by supplying
the "type" parameter to "Imager::Font->new()"
· description - a brief description of the font driver. Defaults
to the value supplied in "class".
AUTHOR
Arnar M. Hrafnkelsson, addi@umich.edu And a great deal of help from
others - see the README for a complete list.
BUGS
The $pos_width member returned by the bounding_box() method has
historically returned different values from different drivers. The
FreeType 1.x and 2.x, and the Win32 drivers return the max of the
advance width and the right edge of the right-most glyph. The Type 1
driver always returns the right edge of the right-most glyph.
The newer advance_width and right_bearing values allow access to any of
the above.
REVISION
$Revision$
SEE ALSOImager(3), Imager::Font::FreeType2(3), Imager::Font::Type1(3),
Imager::Font::Win32(3), Imager::Font::Truetype(3),
Imager::Font::BBox(3)
http://imager.perl.org/
perl v5.14.3 2012-09-28 Imager::Font(3)
