NAME¶
PostScript::TextBlock - An object that may be used to construct a block of
text in PostScript.
SYNOPSIS¶
use PostScript::TextBlock;
my $tb = new PostScript::TextBlock;
$tb->addText( text => "Hullaballo in Hoosick Falls.\n",
font => 'CenturySchL-Ital',
size => 24,
leading => 26
);
$tb->addText( text => "by Charba Gaspee.\n",
font => 'URWGothicL-Demi',
size => 12,
leading => 14
);
print 'There are '.$tb->numElements.' elements in this object.';
open OUT, '>psoutput.ps';
my ($code, $remainder) = $tb->Write(572, 752, 20, 772);
print OUT $code;
DESCRIPTION¶
The PostScript::TextBlock module implements four methods:
- new() - Create a New PostScript::TextBlock
object
- This method instantiates a new object of class
PostScript::TextBlock.
- addText( text=>$text, [ font=>$font ], [
size=>$size ], [ leading=>$leading ] )
- The addText() method will add a new 'text element'
to the TextBlock object. A 'text element' can be thought of as a section
of text that has the same characteristics, i.e. all the characters are the
same font, size and leading. this representation allows you to include
text rendered in multiple fonts at multiple sizes within the same text
block by including them as separate elements.
This method takes up to four attributes (note that the '[]' brackets above
indicate that a parameter is optional, not an array reference):
text The text attribute is required, though nothing bad will happen if you
leave it out. This is simply the text to be rendered in the text block.
Line breaks may be inserted by including a newline "\n".
font The font attribute is a string indicating the name of the font to be
used to render this element. The PS package uses an internal description
of the Font Metrics of various fonts that is contained in the
PostScript::Metrics module. As of this writing, the PostScript::Metrics
module supports the following fonts (basically, the default GhostScript
fonts that have AFM files):
NimbusSanL-ReguCond URWGothicL-Book CenturySchL-Bold CharterBT-Italic
URWBookmanL-Ligh CharterBT-BoldItalic NimbusRomNo9L-ReguItal
URWBookmanL-DemiBoldItal CharterBT-Roman NimbusMonL-ReguObli
NimbusSanL-ReguCondItal CenturySchL-Ital CenturySchL-BoldItal
URWPalladioL-Roma URWBookmanL-LighItal CharterBT-Bold NimbusSanL-BoldCond
NimbusMonL-BoldObli NimbusSanL-BoldCondItal URWGothicL-DemiObli
NimbusSanL-Regu URWPalladioL-Bold NimbusMonL-Regu NimbusSanL-ReguItal
URWGothicL-BookObli URWPalladioL-Ital
You can get a list of the currently supported fonts with the following:
use PostScript::Metrics;
@okfonts = PostScript::Metrics->listFonts();
NOTE: The font must be available to the PostScript interpreter that is used
to render the page described by the program. If the interpreter cannot
load the font, it will ususally attempt to substitute a similar font. If a
font is substituted with a font with different metrics, lines of text may
overrun the right margin of the text block. You have been warned.
It is very easy to create stylesheets for a document:
# Define the styles
#
%body = ( font => 'URWGothicL-DemiObli', size => 12, leading => 16 );
%head1 = ( font => 'NimbusSanL-BoldCond', size => 24, leading => 36 );
%head2 = ( font => 'NimbusSanL-BoldCond', size => 18, leading => 30 );
# Use them where appropriate
#
$tb->addText(text => "Chapter 10\n", %head1);
$tb->addText(text => "Spokane Sam and His Spongepants\n", %head2);
$tb->addText(text => "It was a dark and stormy night and Spokane Sam\'s
Spongepants were thirsty...", %body);
- numElements()
- Returns the number of elements in the text block object. An
'element' is created each time the addText() method is called.
- Write( $width, $height, $xoffset, $yoffset )
- The Write() method will generate the PostScript code
that will render the text on a page when passed to a PostScript
interpreter such as Ghostscript. The four parameters are expressed in
points (1/72 inch) and indicate the width and height of the box within
which the text should be printed, and the x and y offset of the upper left
corner of this box.
Important: PostScript defines the orgin (0,0) as the lower left corner of
the page! This *will* mess you up.
Standard page sizes in points are:
Paper Size Width, Height (in points)
......................... .........................
Letter 612, 792
Legal 612, 1008
Ledger 1224, 792
Tabloid 792, 1224
A0 2384, 3370
A1 1684, 2384
A2 1191, 1684
A3 842, 1191
A4 595, 842
A5 420, 595
A6 297, 420
A7 210, 297
A8 148, 210
A9 105, 148
B0 2920, 4127
B1 2064, 2920
B2 1460, 2064
B3 1032, 1460
B4 729, 1032
B5 516, 729
B6 363, 516
B7 258, 363
B8 181, 258
B9 127, 181
B10 91, 127
#10 Envelope 297, 684
C5 Envelope 461, 648
DL Envelope 312, 624
Folio 595, 935
Executive 522, 756
The write() method returns two values: a string consisting of the
PostScript code (suitable for printing to a file), and a TextBlock object
containing the elements (and partial elements) that did not fit within the
specified area, if any. If the entire text block fits with the area, the
remainder will be undef. The remainder can be used to layout multiple
pages and columns, etc. in a similar manner to most modern desktop
publishing programs. In general, the write() method should be
called as in the following, which writes the PostScript code to a file
called 'psoutput.ps':
open OUT, '>psoutput.ps';
my ($code, $remainder) = $tb->Write(572, 752, 20, 772);
print OUT $code;
To print an entire text block that spans multiple pages, you could do
something like this:
(add enough text to the text block first..)
open OUT, '>psoutput.ps';
my $pages = 1;
# Create the first page
#
my ($code, $remainder) = $tb->Write(572, 752, 20, 772);
print OUT "%%Page:$pages\n"; # this is required by the Adobe
# Document Structuring Conventions
print OUT $code;
print OUT "showpage\n";
# Print the rest of the pages, if any
#
while ($remainder->numElements) {
$pages++;
print OUT "%%Page:$pages\n";
($code, $remainder) = $remainder->Write(572, 752, 20, 772);
print OUT $code;
print OUT "showpage\n";
}
However, if you use the PostScript::Document module to construct generic
multi-page PostScript documents, you don't have to worry about this.
A NOTE ABOUT FONT METRICS¶
The
write() method uses the module PostScript::Metrics to determine the
width of each character; widths vary from font to font and character to
character. If you were writing a stright PostScript program, you would let the
PostScript interpreter do this for you, but in the case of this program, we
need to know the width of each character in a font within the Perl script. The
PostScript::Metrics module contains the font metrics (i.e., a list containing
the width of each character in the font) for a bunch of fonts that are listed
above under the description of the
addText() method. This set started
with the metrics for all of the default fonts with AFM files that came with
GhostScript. It is slowly growing as more fonts are mapped. To add support for
a new font, you must create the array with the metrics for that font and add
it to the PostScript::Metrics module. For a font with an AFM file, the AFM
file can be parsed with Gisle Aas' Font::AFM module, available on CPAN.
Please send all PostScript::Metrics patches to the author at shawn@as220.org.
TODO¶
* better compliance with Adobe's Document Structuring Conventions * more font
metrics descriptions * make font loading code smarter and more efficient for
the interpreter * support a larger character set * it would be nice to add
more functions, e.g.
Clone() * how about settable defaults?
AUTHOR¶
Copyright 1998, 1999 Shawn Wallace. All rights reserved.
Contact the author: shawn@as220.org
http://www.as220.org/shawn
Portions of code contributed by Dan Smeltz.
This is free software. You may use, modify, and redistribute this package under
the same terms as Perl itself.
PostScript is a trademark of Adobe Systems.
