Arnar Mar Hrafnkelsson > Imager-0.43 > Imager::Font

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NAME ^

Imager::Font - Font handling for Imager.

SYNOPSIS ^

  $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) = $font->bounding_box(string=>"Foo");

  $logo = $font->logo(text   => "Slartibartfast Enterprises",
                      size   => 40,
                      border => 5,
                      color  => $green);
  # logo is proposed - doesn't exist yet


  $img->string(font  => $font,
             text  => "Model-XYZ",
             x     => 15,
             y     => 40,
             size  => 40,
             color => $red,
             aa    => 1);

  # Documentation in Imager.pm

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 avaliable 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',
                            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 antialised by default. Imager can see which type of font a file is by looking at the suffix of the filename for the font. A suffix of 'ttf' is taken to mean a truetype font while a suffix of 'pfb' is taken to mean a t1 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');

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

To use Win32 fonts supply the facename 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 contruct the full name of the font as above.

Other logical font attributes may be added if there is sufficient demand.

bounding_box

Returns the bounding box for the specified string. Example:

  my ($neg_width,
      $global_descent,
      $pos_width,
      $global_ascent,
      $descent,
      $ascent,
      $advance_width) = $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.

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 tha 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 indices. This has methods as named above, with some extra convenience methods.

string

This is a method of the Imager class but because it's described in here since it belongs to the font routines. Example:

  $img=Imager->new();
  $img->read(file=>"test.jpg");
  $img->string(font=>$t1font,
               text=>"Model-XYZ",
               x=>0,
               y=>40,
               size=>40,
               color=>$red);
  $img->write(file=>"testout.jpg");

This would put a 40 pixel high text in the top left corner of an image. If you measure the actuall pixels it varies since the fonts usually do not use their full height. It seems that the color and size can be specified twice. When a font is created only the actual font specified matters. It his however convenient to store default values in a font, such as color and size. If parameters are passed to the string function they are used instead of the defaults stored in the font.

The following parameters can be supplied to the string() method:

string

The text to be rendered. If this isn't present the 'text' parameter is used. If neither is present the call will fail.

aa

If non-zero the output will be anti-aliased.

x
y

The start point for rendering the text. See the align parameter.

align

If non-zero the point supplied in (x,y) will be on the base-line, if zero then (x,y) will be at the top-left of the first character.

channel

If present, the text will be written to the specified channel of the image and the color parameter will be ignore.

color

The color to draw the text in.

size

The point-size to draw the text at.

sizew

For drivers that support it, the width to draw the text at. Defaults to be value of the 'size' parameter.

utf8

For drivers that support it, treat the string as UTF8 encoded. For versions of perl that support Unicode (5.6 and later), this will be enabled automatically if the 'string' parameter is already a UTF8 string. See UTF8 for more information.

vlayout

For drivers that support it, draw the text vertically. Note: I haven't found a font that has the appropriate metrics yet.

If string() is called with the channel parameter then the color isn't used and the font is drawn in only one channel of the image. This can be quite handy to create overlays. See the examples for tips about this.

Sometimes it is necessary to know how much space a string takes before rendering it. The bounding_box() method described earlier can be used for that.

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, $bottom, $right) = 
    $font->align(string=>"Hello",
                 x=>100, y=>100, 
                 halign=>'center', valign=>'center', 
                 image=>$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 right end of the text. This will change to the end point of the text (once the proper bounding box interfaces are available).

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 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.

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.

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 UTF8 where the font driver supports UTF8.

Not all fonts support this method (use $font->can("has_chars") to check.)

logo

This method doesn't exist yet but is under consideration. It would mostly be helpful for generating small tests and such. Its proposed interface is:

  $img = $font->logo(string=>"Plan XYZ", color=>$blue, border=>7);

This would be nice for writing (admittedly multiline) one liners like:

Imager::Font->new(file=>"arial.ttf", color=>$blue, aa=>1) ->string(text=>"Plan XYZ", border=>5) ->write(file=>"xyz.png");

face_name()

Returns the internal name of the face. Not all font types support this method yet.

glyph_names(string=>$string [, utf8=>$utf8 ] );

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.

Both Freetype 1.x and 2.x allow support for glyph names to not be included.

UTF8 ^

There are 2 ways of rendering Unicode characters with Imager:

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".

Native UTF8 Support

If your version of perl supports UTF8 and the driver supports UTF8, 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 UTF8 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 UTF8 support, since your string may end up doubly UTF8 encoded.

For example:

 $x = "A\xE2\x80\x90\x41\x{2010}";
 substr($x, -1, 0) = ""; 
 # at this point $x is has the UTF8 flag set, but has 5 characters,
 # none, of which is the constructed UTF8 character

The test script t/t38ft2font.t has a small example of this after the comment:

  # an attempt using emulation of UTF8

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.

The current priority 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 Freetype2 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 Freetype2 support can also do font transformations, you may want to give that a higher priority:

  my @old = Imager::Font->priorities(qw(tt ft2 t1));

AUTHOR ^

Arnar M. Hrafnkelsson, addi@umich.edu And a great deal of help from others - see the README for a complete list.

BUGS ^

You need to modify this class to add new font types.

SEE ALSO ^

Imager(3), Imager::Font::FreeType2(3), Imager::Font::Type1(3), Imager::Font::Win32(3), Imager::Font::Truetype(3), Imager::Font::BBox(3)

http://www.eecs.umich.edu/~addi/perl/Imager/

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