=encoding UTF-8
=head1 NAME
Image::SVG::Path - read the "d" attribute of an SVG path
=head1 SYNOPSIS
use Image::SVG::Path 'extract_path_info';
my $path_d_attribute = "M9.6,20.25c0.61,0.37,3.91,0.45,4.52,0.34c2.86-0.5,14.5-2.09,21.37-2.64c0.94-0.07,2.67-0.26,3.45,0.04";
my @path_info = extract_path_info ($path_d_attribute);
=head1 VERSION
This documents version 0.24 of Image::SVG::Path corresponding to git
commit 9cc7411d91bd2873f926bdb2747ea7e52fd8006f released on Mon Sep 12 11:48:06 2016 +0900.
=head1 DESCRIPTION
This module extracts information contained in the "d" attribute of an
SVG <path> element and turns it into a simpler series of steps.
For example, an SVG <path> element might take the form
<path d="M9.6,20.25c0.61,0.37,3.91,0.45,4.52,0.34c2.86-0.5,14.5-2.09,21.37-2.64c0.94-0.07,2.67-0.26,3.45,0.04"/>
Using an XML parser, such as L<XML::Parser>,
use FindBin '$Bin';
use XML::Parser;
use Image::SVG::Path 'extract_path_info';
my $file = "$Bin/Home_for_the_aged.svg";
my $p = XML::Parser->new (Handlers => {Start => \& start});
$p->parsefile ($file) or die "Error $file: ";
sub start
{
my ($expat, $element, %attr) = @_;
if ($element eq 'path') {
my $d = $attr{d};
my @r = extract_path_info ($d);
for (@r) {
if ($_->{svg_key} =~ /^[mM]$/i) {
print "MOVE TO @{$_->{point}}.\n";
}
}
}
}
produces output
MOVE TO 15 119.
MOVE TO 52 88.
MOVE TO 198 88.
MOVE TO 20 214.
MOVE TO 148 214.
(This example is included as L<F<xml-parser.pl>|https://api.metacpan.org/source/BKB/Image-SVG-Path-0.24/examples/xml-parser.pl> in the distribution.)
SVG means "scalable vector graphics" and it is a standard of the W3
consortium. See L</SVG standards> for details. Although SVG is a type
of XML, the text in the C<d> attribute of SVG paths is not XML but a
condensed form using single letters and numbers. This module is a
parser for that condensed format.
=head1 FUNCTIONS
=head2 extract_path_info
my @path_info = extract_path_info ($path_d_attribute);
Turn the SVG path string into a series of simpler things. For example,
use Image::SVG::Path 'extract_path_info';
my @path_info = extract_path_info ('M6.93,103.36c3.61-2.46,6.65-6.21,6.65-13.29c0-1.68-1.36-3.03-3.03-3.03s-3.03,1.36-3.03,3.03s1.36,3.03,3.03,3.03C15.17,93.1,10.4,100.18,6.93,103.36z');
my $count = 0;
for my $element (@path_info) {
$count++;
print "Element $count:\n";
for my $k (sort keys %$element) {
my $val = $element->{$k};
if (ref $val eq 'ARRAY') {
$val = "[$val->[0], $val->[1]]";
}
print " $k -> $val\n";
}
}
produces output
Element 1:
name -> moveto
point -> [6.93, 103.36]
position -> absolute
svg_key -> M
type -> moveto
Element 2:
control1 -> [3.61, -2.46]
control2 -> [6.65, -6.21]
end -> [6.65, -13.29]
name -> curveto
position -> relative
svg_key -> c
type -> cubic-bezier
Element 3:
control1 -> [0, -1.68]
control2 -> [-1.36, -3.03]
end -> [-3.03, -3.03]
name -> curveto
position -> relative
svg_key -> c
type -> cubic-bezier
Element 4:
control2 -> [-3.03, 1.36]
end -> [-3.03, 3.03]
name -> shorthand/smooth curveto
position -> relative
svg_key -> s
type -> shortcut-cubic-bezier
Element 5:
control2 -> [1.36, 3.03]
end -> [3.03, 3.03]
name -> shorthand/smooth curveto
position -> relative
svg_key -> s
type -> shortcut-cubic-bezier
Element 6:
control1 -> [15.17, 93.1]
control2 -> [10.4, 100.18]
end -> [6.93, 103.36]
name -> curveto
position -> absolute
svg_key -> C
type -> cubic-bezier
Element 7:
name -> closepath
position -> relative
svg_key -> z
type -> closepath
(This example is included as L<F<extract-path-info.pl>|https://api.metacpan.org/source/BKB/Image-SVG-Path-0.24/examples/extract-path-info.pl> in the distribution.)
The return value is a list of hash references. Each hash reference has
at least four keys, C<type>, C<position>, C<name>, and C<svg_key>. The
C<svg_key> field is the original key from the path. The C<type> and
C<name> fields say what the element is, for example a cubic bezier
curve or a line. The C<position> value is either "relative" or
"absolute" depending on whether the coordinates of this step of the
path are relative to the current point (relative) or to the drawing's
origin (absolute). C<position> is relative if C<svg_key> is lower case
and absolute if it is upper case, unless the user chooses the
L</absolute> option.
An option L</no_shortcuts> automatically replaces shortcut cubic
bezier curves with the normal kind, by calculating the first control
point.
A second argument to C<extract_path_info> contains options for the
extraction in the form of a hash reference. For example,
my @path_info = extract_path_info ($path, {absolute => 1});
The following may be chosen by adding them to the hash reference:
=over
=item absolute
If the hash element C<absolute> is set to a true value, relative
positions are changed to absolute. For example a "c" curve is changed
to the equivalent "C" curve. In this case, the C<position> value of
each element's hash is C<absolute>, and C<svg_key> is converted to
upper case.
=item no_shortcuts
If the hash element C<no_shortcuts> is set to a true value then
shortcut cubic bezier curves. ("S" curves) are changed into the
equivalent "C" curves. This only works in combination with the
"absolute" option, otherwise it does nothing. It also does not work
with shortcut quadratic bezier curves.
=item verbose
If this is set to a true value, C<extract_path_info> prints out
informative messages about what it is doing as it parses the path.
=back
=head2 reverse_path
my $reverse_path = reverse_path ($path);
Make an SVG path which is the exact reverse of the input.
This only works for cubic bezier curves with absolute position and no
shortcuts (C elements only). It doesn't fill in all the information
correctly.
use Image::SVG::Path 'reverse_path';
my $path = "M26.75,73c-2.61,6.25-5.49,12.25-8.36,17.15c-0.74,1.26-1.99,1.54-3.23,1.03";
my $reverse = reverse_path ($path);
print "$reverse\n";
produces output
M15.160000,91.180000 C16.400000,91.690000 17.650000,91.410000 18.390000,90.150000 C21.260000,85.250000 24.140000,79.250000 26.750000,73.000000
(This example is included as L<F<test-reverse.pl>|https://api.metacpan.org/source/BKB/Image-SVG-Path-0.24/examples/test-reverse.pl> in the distribution.)
=head2 create_path_string
my $path = create_path_string (\@info);
Given a set of information as created by L</extract_path_info>, turn
them into an SVG string representing a path.
This only works for cubic bezier curves and the initial moveto element
for absolute position and no shortcuts (C elements only).
=head1 SVG path elements
This section documents the output elements. If the path is extracted
using
my @path = extract_path_info ($d);
then the elements of C<@path> are each hash references which contain
one of the following kinds of elements, depending on what is next on
the path.
=head2 Move to elements, M
If C<type> is C<moveto>, the hash reference contains one more field,
C<point>, which is the point to move to. This is an array reference
containing the I<x> and I<y> coordinates as elements indexed 0 and 1
respectively.
=over
=item type
This is C<moveto>.
=item svg_key
This is M or m.
=item point
This is the point to move to.
=back
=head2 Line elements, L
If C<type> is C<lineto>, the hash reference contains one more field,
C<point>, which is the point to move to. This is an array reference
containing the I<x> and I<y> coordinates as elements indexed 0 and 1
respectively.
=over
=item type
This is C<lineto>.
=item svg_key
This is L or l.
=item point
This is the end point of the line.
=item end
This field occurs in some lines for backwards compatibility with
pre-0.16 versions of the module.
=back
=head2 Cubic bezier curve elements, C
If the type is C<cubic-bezier>, the hash reference contains three more
fields, C<control1>, C<control2> and C<end>. The value of each is an
array reference containing the I<x> and I<y> coordinates of the first
and second control points and the end point of the Bezier curve
respectively. (The start point of the curve is the end point of the
previous part of the path.)
=over
=item type
This is C<cubic-bezier>.
=item svg_key
This is C or c.
=item control1
Control point 1 of the curve.
=item control2
Control point 2 of the curve.
=item end
The end point of the curve.
=back
=head2 Shortcut cubic bezier curve elements, S
If the type is C<shortcut-cubic-bezier>, the hash contains two more
fields, C<control2> and C<end>. C<control2> is the second control
point, and C<end> is the end point. The first control point is got by
reflecting the second control point of the previous curve around the
end point of the previous curve (the start point of the current
curve).
Use the L</no_shortcuts> option to automatically convert these into
cubic bezier curve elements.
=over
=item type
This is C<shortcut-cubic-bezier>.
=item svg_key
This is S or s.
=item control2
This is the second control point of the curve (the first one is implicit).
=item end
This is the end point of the curve.
=back
=head2 Quadratic bezier curve elements, Q
If the type is C<quadratic-bezier>, the hash contains two more fields,
C<control> and C<end>. C<control> is the control point, and
C<end> is the end point.
=over
=item type
This is C<quadratic-bezier>.
=item svg_key
This is Q or q.
=item control
This is the control point.
=item end
This is the end point.
=back
=head2 Shortcut quadratic Bezier curves, T
See L<the SVG documentation|/SVG specification> (section 8.3.7) for
how to calculate the control point.
=over
=item type
This is C<shortcut-quadratic-bezier>.
=item svg_key
This is T or t.
=item end
This is the end point.
=back
=head2 Arc elements, A
=over
=item type
This is C<arc>.
=item svg_key
This is C<A> or C<a>.
=item rx, ry
X and Y radiuses
=item x_axis_rotation
See L<the SVG documentation|/SVG specification> (section 8.3.8) for details.
=item large_arc_flag
See L<the SVG documentation|/SVG specification> (section 8.3.8) for details.
=item sweep_flag
See L<the SVG documentation|/SVG specification> (section 8.3.8) for details.
=item x, y
These are the end points of the arc.
=back
Arcs are omitted from L</SVG Tiny>.
=head2 Horizontal line elements, H
Horizontal line elements contain one additional key, C<x>, the
x-coordinate of the end of the line. The y-coordinate is the same as
the y-coordinate of the end point of the previous element.
=over
=item type
This is C<horizontal-line-to>.
=item svg_key
This is H or h.
=item x
This is the x coordinate of the end point. The y coordinate is implicit.
=back
=head2 Vertical line elements, V
Vertical line elements contain one additional key, C<y>, the
y-coordinate of the end of the line. The x-coordinate is the same as
the x-coordinate of the end point of the previous element.
=over
=item type
This is C<vertical-line-to>.
=item svg_key
This is V or v.
=item y
This is the y coordinate of the end point. The x coordinate is implicit.
=back
=head2 Closepath elements, Z
=over
=item type
This is C<closepath>.
=item svg_key
This is Z or z.
=back
Each hash reference also contains the field C<position>, which has
either the value C<absolute> or C<relative> depending on whether
C<svg_key> is upper case or lower case, respectively. A field C<name>
also exists.
=head1 BUGS
=over
=item Does not use the grammar
There is a grammar for the paths in the W3 specification. See
L<https://www.w3.org/TR/SVG/paths.html#PathDataBNF>. However, this
module does not use that grammar. Instead it hacks up the path using
regexes.
=item L</no_shortcuts> does not work with quadratic bezier curves
Currently the L</no_shortcuts> option does not work with quadratic
bezier curves.
=back
=head1 EXPORTS
None of the functions is exported by default.
use Image::SVG::Path ':all';
exports all of L</extract_path_info>, L</reverse_path> and
L</create_path_string>.
=head1 SEE ALSO
=head2 Other CPAN modules
=over
=item L<SVG::Rasterize>
This contains a complete parser for SVG paths in
C<SVG::Rasterize::Engine::PangoCairo>. It is embedded into the module
and is used to draw with L<Cairo>.
=item L<MarpaX::Languages::SVG::Parser>
This parser uses the SVG grammar mentioned in L</BUGS>.
=item L<SVG::Estimate>
This is an application of Image::SVG::Path which uses it to estimate
the lengths of the paths of SVG images.
=item L<Image::CairoSVG>
This is a least-effort module by the same author as Image::SVG::Path
which renders some kinds of SVGs using L<Cairo>.
=item L<Image::LibRSVG>
Render SVG via a Gnome library.
=back
=head2 SVG standards
=over
=item SVG specification
L<The full specification|https://www.w3.org/TR/SVG/> contains all the
details. The L<SVG path
specification|https://www.w3.org/TR/SVG/paths.html> contains the
specifications for paths.
=item SVG Tiny
L<SVG Tiny|http://www.w3.org/TR/SVGTiny12/index.html> is a subset of
SVG. It claims to have a L<Perl Language
Binding|http://www.w3.org/TR/SVGTiny12/perl-binding.html>, but I
cannot locate the source code.
=item SVG basic
There is also another standard, SVG basic, I'm not too sure whether
either this or SVG Tiny are in use.
=back
=head1 ACKNOWLEDGEMENTS
Colin Kuskie (L<http://www.perldreamer.com/>) fixed error messages for
version 0.20, number paths for version 0.21, implicit line-tos for
version 0.22, implicit arc commands for version 0.23, and multiple
closepaths for version 0.24.
=head1 AUTHOR
Ben Bullock, <bkb@cpan.org>
=head2 Request
If you'd like to see this module continued, let me know that you're
using it. For example, send an email, write a bug report, star the
project's github repository, add a patch, add a C<++> on Metacpan.org,
or write a rating at CPAN ratings. It really does make a
difference. Thanks.
=head1 COPYRIGHT & LICENCE
This package and associated files are copyright (C)
2011-2016
Ben Bullock.
You can use, copy, modify and redistribute this package and associated
files under the Perl Artistic Licence or the GNU General Public
Licence.