Provided by: libgd-svg-perl_0.33-1_all 
NAME
GD::SVG - Seamlessly enable SVG output from scripts written using GD
SYNOPSIS
# use GD;
use GD::SVG;
# my $img = GD::Image->new();
my $img = GD::SVG::Image->new();
# $img->png();
$img->svg();
DESCRIPTION
GD::SVG painlessly enables scripts that utilize GD to export scalable vector graphics
(SVG). It accomplishes this task by wrapping SVG.pm with GD-styled method calls. To enable
this functionality, one need only change the "use GD" call to "use GD::SVG" (and initial
"new" method calls).
EXPORTS
GD::SVG exports the same methods as GD itself, overriding those methods.
USAGE
In order to generate SVG output from your script using GD::SVG, you will need to first
# use GD;
use GD::SVG;
After that, each call to the package classes that GD implements should be changed to
GD::SVG. Thus:
GD::Image becomes GD::SVG::Image
GD::Font becomes GD::SVG::Font
DYNAMICALLY SELECTING SVG OUTPUT
If you would like your script to be able to dynamically select either PNG or JPEG output
(via GD) or SVG output (via GD::SVG), you should place your "use" statement within an
eval. In the example below, each of the available classes is created at the top of the
script for convenience, as well as the image output type.
my $package = shift;
eval "use $package";
my $image_pkg = $package . '::Image';
my $font_pkg = $package . '::Font';
# Creating new images thus becomes
my $image = $image_pkg->new($width,$height);
# Establish the image output type
my $image_type;
if ($package = 'GD::SVG') {
$image_type = 'svg';
} else {
$image_type = 'png';
}
Finally, you should change all GD::Image and GD::Font references to $image_pkg-> and
$font_pkg->, respectively.
GD::Image->new() becomes $image_pkg->new()
GD::Font->Large() becomes $font_pkg->Large()
The GD::Polygon and GD::Polyline classes work with GD::SVG without modification.
If you make heavy use of GD's exported methods, it may also be necessary to add () to the
endo of method names to avoide bareword compilation errors. That's the price you pay for
using exported functions!
IMPORTANT NOTES
GD::SVG does not directly generate SVG, but instead relies upon SVG.pm. It is not intended
to supplant SVG.pm. Furthermore, since GD::SVG is, in essence an API to an API, it may
not be suitable for applications where speed is of the essence. In these cases, GD::SVG
may provide a short-term solution while scripts are re-written to enable more direct
output of SVG.
Many of the GD::SVG methods accept additional parameters (which are in turn reflected in
the SVG.pm API) that are not supported in GD. Look through the remainder of this document
for options on specific In addition, several functions have yet to be mapped to SVG.pm
calls. Please see the section below regarding regarding GD functions that are missing or
altered in GD::SVG.
A similar module (SVG::GD) implements a similar wrapper around GD. Please see the section
at the bottom of this document that compares GD::SVG to SVG::GD.
PREREQUISITES
GD::SVG requires the Ronan Oger's SVG.pm module, Lincoln Stein's GD.pm module, libgd and
its dependencies.
GENERAL DIFFICULTIES IN TRANSLATING GD TO SVG
These are the primary weaknesses of GD::SVG.
SVG requires unique identifiers for each element
Each element in an SVG image requires a unique identifier. In general, GD::SVG handles
this by automatically generating unique random numbers. In addition to the typical
parameters for GD methods, GD::SVG methods allow a user to pass an optional id
parameter for naming the object.
Direct calls to the GD package will fail
You must change direct calls to the classes that GD invokes:
GD::Image->new() should be changed to GD::SVG::Image->new()
See the documentation above for how to dynamically switch between packages.
raster fill() and fillToBorder() not supported
As SVG documents are not inherently aware of their canvas, the flood fill methods are
not currently supported.
getPixel() not supported.
Although setPixel() works as expected, its counterpart getPixel() is not supported. I
plan to support this method in a future release.
No support for generation of images from filehandles or raw data
GD::SVG works only with scripts that generate images directly in the code using the
GD->new(height,width) approach. newFrom() methods are not currently supported.
Tiled fills are not supported
Any functions passed gdTiled objects will die.
Styled and Brushed lines only partially implemented
Calls to the gdStyled and gdBrushed functions via a rather humorous kludge (and
simplification). Depending on the complexity of the brush, they may behave from
slightly differently to radically differently from their behavior under GD. You have
been warned. See the documentation sections for the methods that set these options
(setStyle(), setBrush(), and setTransparent()).
See below for a full list of methods that have not yet been implemented.
WHEN THINGS GO WRONG
GD is a complicated module. Translating GD methods into those required to draw in SVG are
not always direct. You may or may not get the output you expect. In general, some tweaking
of image parameters (like text height and width) may be necessary.
If your script doesn't work as expected, first check the list of methods that GD::SVG
provides. Due to differences in the nature of SVG images, not all GD methods have been
implemented in GD::SVG.
If your image doesn't look as expected, try tweaking specific aspects of image generation.
In particular, check for instances where you calculate dimensions of items on the fly like
font->height. In SVG, the values of fonts are defined explicitly.
GD FUNCTIONS MISSING FROM GD::SVG
The following GD functions have not yet been incorporated into GD::SVG. If you attempt to
use one of these functions (and you have enabled debug warnings via the new() method),
GD::SVG will print a warning to STDERR.
Creating image objects:
GD::Image->newPalette([$width,$height])
GD::Image->newTrueColor([$width,$height])
GD::Image->newFromPng($file, [$truecolor])
GD::Image->newFromPngData($data, [$truecolor])
GD::Image->newFromJpeg($file, [$truecolor])
GD::Image->newFromJpegData($data, [$truecolor])
GD::Image->newFromXbm($file)
GD::Image->newFromWMP($file)
GD::Image->newFromGd($file)
GD::Image->newFromGdData($data)
GD::Image->newFromGd2($file)
GD::Image->newFromGd2Data($data)
GD::Image->newFromGd2Part($file,srcX,srcY,width,height)
GD::Image->newFromXpm($filename)
Image methods:
$gddata = $image->gd
$gd2data = $image->gd2
$wbmpdata = $image->wbmp([$foreground])
Color control methods:
$image->colorAllocateAlpha()
$image->colorClosest()
$image->colorClosestHWB()
$image->getPixel()
$image->transparent()
Special Colors:
$image->setBrush() (semi-supported, with kludge)
$image->setStyle() (semi-supported, with kludge)
gdTiled
$image->setAntialiased()
gdAntiAliased()
$image->setAntiAliasedDontBlend()
Drawing methods:
$image->dashedLine()
$image->fill()
$image->fillToBorder()
Image copying methods
None of the image copying methods are yet supported
Image transformation methods
None of the image transformation methods are yet supported
Character and string drawing methods
$image->stringUp() - incompletely supported - broken
$image->charUp()
$image->stringFT()
Alpha Channels
$image->alphaBlending()
$image->saveAlpha()
Miscellaneous image methods
$image->isTrueColor()
$image->compare($image2)
$image->clip()
$image->boundsSafe()
GD::Polyline
Supported without modifications
Font methods:
$font->nchars()
$font->offset()
GROUPING FUNCTIONS GD::SVG
GD::SVG supports three additional methods that provides the ability to recursively group
objects:
$this->startGroup([$id,\%style]), $this->endGroup()
These methods start and end a group in a procedural manner. Once a group is started,
all further drawing will be appended to the group until endGroup() is invoked. You may
optionally pass a string ID and an SVG styles hash to startGroup.
$group = $this->newGroup([$id,\%style])
This method returns a GD::Group object, which has all the behaviors of a GD::SVG
object except that it draws within the current group. You can invoke this object's
drawing methods to draw into a group. The group is closed once the object goes out of
scope. While the object is open, invoking drawing methods on the parent GD::SVG object
will also draw into the group until it goes out of scope.
Here is an example of using grouping in the procedural way:
use GD::SVG;
my $img = GD::SVG::Image->new(500,500);
my $white = $img->colorAllocate(255,255,255);
my $black = $img->colorAllocate(0,0,0);
my $blue = $img->colorAllocate(0,0,255);
my $red = $img->colorAllocate(255,0,0);
$img->startGroup('circle in square');
$img->rectangle(100,100,400,400,$blue);
$img->startGroup('circle and boundary');
$img->filledEllipse(250,250,200,200,$red);
$img->ellipse(250,250,200,200,$black);
$img->endGroup;
$img->endGroup;
print $img->svg;
Here is an example of using grouping with the GD::Group object:
...
my $g1 = $img->newGroup('circle in square');
$g1->rectangle(100,100,400,400,$blue);
my $g2 = $g1->startGroup('circle and boundary');
$g2->filledEllipse(250,250,200,200,$red);
$g2->ellipse(250,250,200,200,$black);
print $img->svg;
Finally, here is a fully worked example of using the GD::Simple module to make the
syntax cleaner:
#!/usr/bin/perl
use strict;
use GD::Simple;
GD::Simple->class('GD::SVG');
my $img = GD::Simple->new(500,500);
$img->bgcolor('white');
$img->fgcolor('blue');
my $g1 = $img->newGroup('circle in square');
$g1->rectangle(100,100,400,400);
$g1->moveTo(250,250);
my $g2 = $g1->newGroup('circle and boundary');
$g2->fgcolor('black');
$g2->bgcolor('red');
$g2->ellipse(200,200);
print $img->svg;
GD VERSUS GD::SVG METHODS
All GD::SVG methods mimic the naming and interface of GD methods. As such, maintenance of
GD::SVG follows the development of both GD and SVG. Much of the original GD documentation
is replicated here for ease of use. Subtle differences in the implementation of these
methods between GD and GD::SVG are discussed below. In particular, the return value for
some GD::SVG methods differs from its GD counterpart.
OBJECT CONSTRUCTORS: CREATING IMAGES
GD::SVG currently only supports the creation of image objects via its new constructor.
This is in contrast to GD proper which supports the creation of images from previous
images, filehandles, filenames, and data.
$image = GD::SVG::Image->new($height,$width,$debug);
Create a blank GD::SVG image object of the specified dimensions in pixels. In turn,
this method will create a new SVG object and store it internally. You can turn on
debugging with the GD::SVG specific $debug parameter. This should be boolean true and
will cause non-implemented methods to print a warning on their status to STDERR.
GD::SVG::Image METHODS
Once a GD::Image object is created, you can draw with it, copy it, and merge two images.
When you are finished manipulating the object, you can convert it into a standard image
file format to output or save to a file.
Image Data Output Methods
GD::SVG implements a single output method, svg()!
$svg = $image->svg();
This returns the image in SVG format. You may then print it, pipe it to an image
viewer, or write it to a file handle. For example,
$svg_data = $image->svg();
open (DISPLAY,"| display -") || die;
binmode DISPLAY;
print DISPLAY $svg_data;
close DISPLAY;
if you'd like to return an inline version of the image (instead of a full document
version complete with the DTD), pass the svg() method the 'inline' flag:
$svg_data = $image->svg(-inline=>'true');
Calling the other standard GD image output methods (eg jpeg,gd,gd2,png) on a
GD::SVG::Image object will cause your script to exit with a warning.
Color Control
These methods allow you to control and manipulate the color table of a GD::SVG image. In
contrast to GD which uses color indices, GD::SVG passes stringified RGB triplets as
colors. GD::SVG, however, maintains an internal hash structure of colors and colored
indices in order to map GD functions that manipulate the color table. This typically
requires behind-the-scenes translation of these stringified RGB triplets into a color
index.
$stringified_color = $image->colorAllocate(RED,GREEN,BLUE)
Unlike GD, colors need not be allocated in advance in SVG. Unlike GD which returns a
color index, colorAllocate returns a formatted string compatible with SVG.
Simultaneously, it creates and stores internally a GD compatible color index for use
with GD's color manipulation methods.
returns: "rgb(RED,GREEN,BLUE)"
$index = $image->colorAllocateAlpha()
NOT IMPLEMENTED
$image->colorDeallocate($index)
Provided with a color index, remove it from the color table.
$index = $image->colorClosest(red,green,blue)
This returns the index of the color closest in the color table to the red green and
blue components specified. This method is inherited directly from GD.
Example: $apricot = $myImage->colorClosest(255,200,180);
NOT IMPLEMENTED
$index = $image->colorClosestHWB(red,green,blue)
NOT IMPLEMENTED
$index = $image->colorExact(red,green,blue)
Retrieve the color index of an rgb triplet (or -1 if it has yet to be allocated).
NOT IMPLEMENTED
$index = $image->colorResolve(red,green,blue)
NOT IMPLEMENTED
$colors_total = $image->colorsTotal()
Retrieve the total number of colors indexed in the image.
$index = $image->getPixel(x,y)
NOT IMPLEMENTED
($red,$green,$blue) = $image->rgb($index)
Provided with a color index, return the RGB triplet. In GD::SVG, color indexes are
replaced with actual RGB triplets in the form "rgb($r,$g,$b)".
$image->transparent($colorIndex);
Control the transparency of individual colors.
NOT IMPLEMENTED
Special Colors
GD implements a number of special colors that can be used to achieve special effects.
They are constants defined in the GD:: namespace, but automatically exported into your
namespace when the GD module is loaded. GD::SVG offers limited support for these methods.
$image->setBrush($brush) (KLUDGE ALERT)
gdBrushed
In GD, one can draw lines and shapes using a brush pattern. Brushes are just images
that you can create and manipulate in the usual way. When you draw with them, their
contents are used for the color and shape of the lines.
To make a brushed line, you must create or load the brush first, then assign it to the
image using setBrush(). You can then draw in that with that brush using the gdBrushed
special color. It's often useful to set the background of the brush to transparent so
that the non-colored parts don't overwrite other parts of your image.
# Via GD, this is how one would set a Brush
$diagonal_brush = new GD::Image(5,5);
$white = $diagonal_brush->colorAllocate(255,255,255);
$black = $diagonal_brush->colorAllocate(0,0,0);
$diagonal_brush->transparent($white);
$diagonal_brush->line(0,4,4,0,$black); # NE diagonal
GD::SVG offers limited support for setBrush (and the corresponding gdBrushed methods)
- currently only in the shapes of squares. Internally, GD::SVG extracts the longest
dimension of the image using the getBounds() method. Next, it extracts the second
color set, assuming that to be the foreground color. It then re-calls the original
drawing method with these new values in place of the gdBrushed. See the private
_distill_gdSpecial method for the internal details of this operation.
$image->setThickness($thickness)
Lines drawn with line(), rectangle(), arc(), and so forth are 1 pixel thick by
default. Call setThickness() to change the line drawing width.
$image->setStyle(@colors)
setStyle() and gdStyled() are partially supported in GD::SVG. GD::SVG determines the
alternating pattern of dashes, treating the first unique color encountered in the
array as on, the second as off and so on. The first color in the array is then used to
draw the actual line.
gdTiled
NOT IMPLEMENTED
gdStyled()
The GD special color gdStyled is partially implemented in GD::SVG. Only the first
color will be used to generate the dashed pattern specified in setStyle(). See
setStyle() for additional information.
$image->setAntiAliased($color)
NOT IMPLEMENTED
gdAntiAliased
NOT IMPLEMENTED
$image->setAntiAliasedDontBlend($color,[$flag])
NOT IMPLEMENTED
Drawing Commands
$image->setPixel($x,$y,$color)
Set the corresponding pixel to the given color. GD::SVG implements this by drawing a
single dot in the specified color at that position.
$image->line(x1,y1,x2,y2,color);
Draw a line between the two coordinate points with the specified color. Passing an
optional id will set the id of that SVG element. GD::SVG also supports drawing with
the special brushes - gdStyled and gdBrushed - although these special styles are
difficult to replicate precisley in GD::SVG.
$image->dashedLine($x1,$y1,$x2,$y2,$color);
NOT IMPLEMENTED
$image->rectangle($x1,$y1,$x2,$y2,$color);
This draws a rectangle with the specified color. (x1,y1) and (x2,y2) are the upper
left and lower right corners respectively. You may also draw with the special colors
gdBrushed and gdStyled.
$image->filledRectangle($x1,$y1,$x2,$y2,$color);
filledRectangle is a GD specific method with no direct equivalent in SVG. GD::SVG
translates this method into an SVG appropriate method by passing the filled color
parameter as a named 'filled' parameter to SVG. Drawing with the special colors is
also permitted. See the documentation for the line() method for additional details.
GD call:
$img->filledRectangle($x1,$y1,$x2,$y2,$color);
SVG call:
$img->rectangle(x=> $x1,y=> $y1,
width => $x2-$x1,
height => $y2-$y1,
fill => $color
$image->polygon($polygon,$color);
This draws a polygon with the specified color. The polygon must be created first (see
"Polygons" below). The polygon must have at least three vertices. If the last vertex
doesn't close the polygon, the method will close it for you. Both real color indexes
and the special colors gdBrushed, gdStyled and gdStyledBrushed can be specified. See
the documentation for the line() method for additional details.
$poly = new GD::Polygon;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
$image->polygon($poly,$blue);
$image->filledPolygon($polygon,$color);
This draws a polygon filled with the specified color. Drawing with the special colors
is also permitted. See the documentation for the line() method for additional details.
# make a polygon
$poly = new GD::Polygon;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
# draw the polygon, filling it with a color
$image->filledPolygon($poly,$peachpuff);
$image->filledPolygon($polygon,$color);
This draws a polygon filled with the specified color. Drawing with the special colors
is also permitted. See the documentation for the line() method for additional details.
# make a polygon
$poly = new GD::Polygon;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
# draw the polygon, filling it with a color
$image->filledPolygon($poly,$peachpuff);
$image->polyline(polyline,color)
$image->polyline($polyline,$black)
This draws a polyline with the specified color. Both real color indexes and the
special colors gdBrushed, gdStyled and gdStyledBrushed can be specified.
Neither the polyline() method or the polygon() method are very picky: you can call
either method with either a GD::Polygon or a GD::Polyline. The method determines if
the shape is "closed" or "open" as drawn, not the object type.
$image->polydraw(polything,color)
$image->polydraw($poly,$black)
This method draws the polything as expected (polygons are closed, polylines are open)
by simply checking the object type and calling either $image->polygon() or
$image->polyline().
$image->ellipse($cx,$cy,$width,$height,$color)
$image->filledEllipse($cx,$cy,$width,$height,$color)
These methods() draw ellipses. ($cx,$cy) is the center of the arc, and
($width,$height) specify the ellipse width and height, respectively. filledEllipse()
is like ellipse() except that the former produces filled versions of the ellipse.
Drawing with the special colors is also permitted. See the documentation for the
line() method for additional details.
$image->arc($cy,$cy,$width,$height,$start,$end,$color);
This draws arcs and ellipses. (cx,cy) are the center of the arc, and (width,height)
specify the width and height, respectively. The portion of the ellipse covered by the
arc are controlled by start and end, both of which are given in degrees from 0 to 360.
Zero is at the top of the ellipse, and angles increase clockwise. To specify a
complete ellipse, use 0 and 360 as the starting and ending angles. To draw a circle,
use the same value for width and height.
Internally, arc() calls the ellipse() method of SVG.pm. Drawing with the special
colors is also permitted. See the documentation for the line() method for additional
details.
Currently, true arcs are NOT supported, only those where the start and end equal 0 and
360 respectively resulting in a closed arc.
$image->filledArc($cx,$cy,$width,$height,$start,$end,$color [,$arc_style])
This method is like arc() except that it colors in the pie wedge with the selected
color. $arc_style is optional. If present it is a bitwise OR of the following
constants:
gdArc connect start & end points of arc with a rounded edge gdChord
connect start & end points of arc with a straight line gdPie synonym for
gdChord gdNoFill outline the arc or chord gdEdged connect beginning and
ending of the arc to the center
gdArc and gdChord are mutally exclusive. gdChord just connects the starting and
ending angles with a straight line, while gdArc pro- duces a rounded edge. gdPie is a
synonym for gdArc. gdNoFill indi- cates that the arc or chord should be outlined, not
filled. gdEdged, used together with gdNoFill, indicates that the beginning and ending
angles should be connected to the center; this is a good way to outline (rather than
fill) a "pie slice."
Using these special styles, you can easily draw bordered ellipses and circles.
# Create the filled shape: $image->filledArc($x,$y,$width,$height,0,360,$fill); # Now
border it. $image->filledArc($x,$y,$width,$height,0,360,$color,gdNoFill);
$image->fill();
NOT IMPLEMENTED
$image->fillToBorder()
NOT IMPLEMENTED
Image Copying Methods
The basic copy() command is implemented in GD::SVG. You can copy one GD::SVG into another
GD::SVG, or copy a GD::Image or GD::Simple object into a GD::SVG, thereby embedding a
pixmap image into the SVG image.
All other image copying methods are unsupported, and if your script calls one of the
following methods, your script will die remorsefully with a warning. With sufficient
demand, I might try to implement some of these methods. For now, I think that they are
beyond the intent of GD::SVG.
$image->clone()
$image->copyMerge()
$image->copyMergeGray()
$image->copyResized()
$image->copyResampled()
$image->trueColorToPalette()
Image Transfomation Commands
None of the image transformation commands are implemented in GD::SVG. If your script
calls one of the following methods, your script will die remorsefully with a warning.
With sufficient demand, I might try to implement some of these methods. For now, I think
that they are beyond the intent of GD::SVG.
$image = $sourceImage->copyRotate90()
$image = $sourceImage->copyRotate180()
$image = $sourceImage->copyRotate270()
$image = $sourceImage->copyFlipHorizontal()
$image = $sourceImage->copyFlipVertical()
$image = $sourceImage->copyTranspose()
$image = $sourceImage->copyReverseTranspose()
$image->rotate180()
$image->flipHorizontal()
$image->flipVertical()
Character And String Drawing
GD allows you to draw characters and strings, either in normal horizon- tal orientation or
rotated 90 degrees. In GD, these routines use a GD::Font object. Internally, GD::SVG
mimics the behavior of GD with respect to fonts in a very similar manner, using instead a
GD::SVG::Font object described in more detail below.
GD's font handling abilities are not as flexible as SVG and it does not allow the dynamic
creation of fonts, instead exporting five available fonts as global variables:
gdGiantFont, gdLargeFont, gdMediumBoldFont, gdSmallFont and gdTinyFont. GD::SVG also
exports these same global variables but establishes them in a different manner using
constant variables to establish the font family, font height and width of these global
fonts. These values were chosen to match as closely as possible GD's output. If
unsatisfactory, adjust the constants at the top of this file. In all subroutines below,
GD::SVG passes a generic GD::SVG::Font object in place of the exported font variables.
$image->string($font,$x,$y,$string,$color)
This method draws a string starting at position (x,y) in the speci- fied font and
color. Your choices of fonts are gdSmallFont, gdMediumBoldFont, gdTinyFont,
gdLargeFont and gdGiantFont.
$myImage->string(gdSmallFont,2,10,"Peachy Keen",$peach);
$image->stringUp($font,$x,$y,$string,$color)
Same as the previous example, except that it draws the text rotated counter-clockwise
90 degrees.
$image->char($font,$x,$y,$char,$color)
$image->charUp($font,$x,$y,$char,$color)
These methods draw single characters at position (x,y) in the spec- ified font and
color. They're carry-overs from the C interface, where there is a distinction between
characters and strings. Perl is insensible to such subtle distinctions. Neither is
SVG, which simply calls the string() method internally.
@bounds = $image->stringFT($fgcolor,$font- name,$ptsize,$angle,$x,$y,$string)
@bounds = $image->stringFT($fgcolor,$font- name,$ptsize,$angle,$x,$y,$string,\%options)
In GD, these methods use TrueType to draw a scaled, antialiased strings using the
TrueType font of your choice. GD::SVG can handle this directly generating by calling
the string() method internally.
The arguments are as follows:
fgcolor Color index to draw the string in
fontname An absolute path to the TrueType (.ttf) font file
ptsize The desired point size (may be fractional)
angle The rotation angle, in radians
x,y X and Y coordinates to start drawing the string
string The string itself
GD::SVG attempts to extract the name of the font from the pathname supplied in the
fontname argument. If it fails, Helvetica will be used instead.
If successful, the method returns an eight-element list giving the boundaries of the
rendered string:
@bounds[0,1] Lower left corner (x,y)
@bounds[2,3] Lower right corner (x,y)
@bounds[4,5] Upper right corner (x,y)
@bounds[6,7] Upper left corner (x,y)
This from the GD documentation (not yet implemented in GD::SVG):
An optional 8th argument allows you to pass a hashref of options to stringFT(). Two
hashkeys are recognized: linespacing, if present, controls the spacing between lines
of text. charmap, if present, sets the character map to use.
The value of linespacing is supposed to be a multiple of the char- acter height, so
setting linespacing to 2.0 will result in double- spaced lines of text. However the
current version of libgd (2.0.12) does not do this. Instead the linespacing seems to
be double what is provided in this argument. So use a spacing of 0.5 to get
separation of exactly one line of text. In practice, a spacing of 0.6 seems to give
nice results. Another thing to watch out for is that successive lines of text should
be separated by the "\r\n" characters, not just "\n".
The value of charmap is one of "Unicode", "Shift_JIS" and "Big5". The interaction
between Perl, Unicode and libgd is not clear to me, and you should experiment a bit if
you want to use this feature.
$gd->stringFT($black,'/dosc/windows/Fonts/pala.ttf',40,0,20,90,
"hi there\r\nbye now",
{linespacing=>0.6,
charmap => 'Unicode',
});
For backward compatibility with older versions of the FreeType library, the alias
stringTTF() is also recognized. Also be aware that relative font paths are not
recognized due to problems in the libgd library.
$hasfontconfig = $image->useFontConfig($flag)
Call useFontConfig() with a value of 1 in order to enable support for fontconfig font
patterns (see stringFT). Regardless of the value of $flag, this method will return a
true value if the fontconfig library is present, or false otherwise.
NOT IMPLEMENTED
Alpha Channels
$image->alphaBlending($blending)
NOT IMPLEMENTED
$image->saveAlpha($saveAlpha)
NOT IMPLEMENTED
Miscellaneous Image Methods
$image->interlaced([$flag])
NOT IMPLEMENTED
($width,$height) = $image->getBounds()
getBounds() returns the height and width of the image.
$is_truecolor = $image->isTrueColor()
NOT IMPLEMENTED
$flag = $image1->compare($image2)
NOT IMPLEMENTED
$image->clip($x1,$y1,$x2,$y2) ($x1,$y1,$x2,$y2) = $image->clip
NOT IMPLEMENTED
$flag = $image->boundsSafe($x,$y)
NOT IMPLEMENTED
GD::SVG::Polygon METHODS
SVG is much more adept at creating polygons than GD. That said, GD does provide some
rudimentary support for polygons but must be created as seperate objects point by point.
$poly = GD::SVG::Polygon->new
Create an empty polygon with no vertices.
$poly = new GD::SVG::Polygon;
$poly->addPt($x,$y)
Add point (x,y) to the polygon.
$poly->addPt(0,0);
$poly->addPt(0,50);
$poly->addPt(25,25);
($x,$y) = $poly->getPt($index)
Retrieve the point at the specified vertex.
($x,$y) = $poly->getPt(2);
$poly->setPt($index,$x,$y)
Change the value of an already existing vertex. It is an error to set a vertex that
isn't already defined.
$poly->setPt(2,100,100);
($x,$y) = $poly->deletePt($index)
Delete the specified vertex, returning its value.
($x,$y) = $poly->deletePt(1);
$poly->toPt($dx,$dy)
Draw from current vertex to a new vertex, using relative (dx,dy) coordinates. If this
is the first point, act like addPt().
$poly->addPt(0,0);
$poly->toPt(0,50);
$poly->toPt(25,-25);
NOT IMPLEMENTED
$vertex_count = $poly->length()
Return the number of vertices in the polygon.
@vertices = $poly->vertices()
Return a list of all the verticies in the polygon object. Each mem- ber of the list
is a reference to an (x,y) array.
@vertices = $poly->vertices;
foreach $v (@vertices)
print join(",",@$v),"\n";
}
@rect = $poly->bounds()
Return the smallest rectangle that completely encloses the polygon. The return value
is an array containing the (left,top,right,bottom) of the rectangle.
($left,$top,$right,$bottom) = $poly->bounds;
$poly->offset($dx,$dy)
Offset all the vertices of the polygon by the specified horizontal (dh) and vertical
(dy) amounts. Positive numbers move the polygon down and to the right. Returns the
number of vertices affected.
$poly->offset(10,30);
$poly->map($srcL,$srcT,$srcR,$srcB,$destL,$dstT,$dstR,$dstB)
Map the polygon from a source rectangle to an equivalent position in a destination
rectangle, moving it and resizing it as necessary. See polys.pl for an example of how
this works. Both the source and destination rectangles are given in
(left,top,right,bottom) coordi- nates. For convenience, you can use the polygon's own
bounding box as the source rectangle.
# Make the polygon really tall
$poly->map($poly->bounds,0,0,50,200);
NOT IMPLEMENTED
$poly->scale($sx,$sy)
Scale each vertex of the polygon by the X and Y factors indicated by sx and sy. For
example scale(2,2) will make the polygon twice as large. For best results, move the
center of the polygon to position (0,0) before you scale, then move it back to its
previous position.
NOT IMPLEMENTED
$poly->transform($sx,$rx,$sy,$ry,$tx,$ty)
Run each vertex of the polygon through a transformation matrix, where sx and sy are
the X and Y scaling factors, rx and ry are the X and Y rotation factors, and tx and ty
are X and Y offsets. See the Adobe PostScript Reference, page 154 for a full
explanation, or experiment.
NOT IMPLEMENTED
GD::Polyline
Please see GD::Polyline for information on creating open polygons and splines.
GD::SVG::Font METHODS
NOTE: The object-oriented implementation to font utilites is not yet supported.
The libgd library (used by the Perl GD library) has built-in support for about half a
dozen fonts, which were converted from public-domain X Windows fonts. For more fonts,
compile libgd with TrueType support and use the stringFT() call.
GD::SVG replicates the internal fonts of GD by hardcoding fonts which resemble the design
and point size of the original. Each of these fonts is available both as an imported
global (e.g. gdSmallFont) and as a package method (e.g. GD::Font->Small).
gdTinyFont
GD::Font->Tiny
This is a tiny, almost unreadable font, 5x8 pixels wide.
gdSmallFont
GD::Font->Small
This is the basic small font, "borrowed" from a well known public domain 6x12 font.
gdMediumBoldFont
GD::Font->MediumBold
This is a bold font intermediate in size between the small and large fonts, borrowed
from a public domain 7x13 font;
gdLargeFont
GD::Font->Large
This is the basic large font, "borrowed" from a well known public domain 8x16 font.
gdGiantFont
GD::Font->Giant
This is a 9x15 bold font converted by Jan Pazdziora from a sans serif X11 font.
$font->nchars
This returns the number of characters in the font.
print "The large font contains ",gdLargeFont->nchars," characters\n";
NOT IMPLEMENTED
$font->offset()
This returns the ASCII value of the first character in the font
$width = $font->width
$height = $font->height
These return the width and height of the font.
($w,$h) = (gdLargeFont->width,gdLargeFont->height);
REAL WORLD EXAMPLES
BioPerl
The Bio::Graphics package of the BioPerl project makes use of GD::SVG to export SVG
graphics.
http://www.bioperl.org/
Generic Genome Browser
The Generic Genome Browser (GBrowse) utilizes Bio::Graphics and enables SVG dumping of
genomics views. You can see a real-world example of SVG output from GBrowse at
WormBase:
http://www.wormbase.org/cgi-bin/gbrowse/
Further information about the Generic Genome Browser is available at the Generic Model
Organism Project home page:
http://www.gmod.org/
toddot
I've also prepared a number of comparative images at my website (shameless plug,
hehe):
http://www.toddot.net/projects/GD-SVG/
INTERNAL METHODS
The following internal methods are private and documented only for those wishing to extend
the GD::SVG interface.
_distill_gdSpecial()
When a drawing method is passed a stylized brush via gdBrushed, the internal
_distill_gdSpecial() method attempts to make sense of this by setting line thickness
and foreground color. Since stylized brushes are GD::SVG::Image objects, it does this
by fetching the width of the image using the getBounds method. This width is then used
to setThickness. The last color set by colorAllocate is then used for the foreground
color.
In setting line thickness, GD::SVG temporarily overrides any previously set line
thickness. In GD, setThickness is persistent through uses of stylized brushes. To
accomodate this behavior, _distill_gdSpecial() temporarily stores the previous
line_thickness in the $self->{previous_line_thickness} flag.
_reset()
The _reset() method is used to restore persistent drawing settings between uses of
stylized brushes. Currently, this involves
- restoring line thickness
IMPORTANT NOTE! GD::SVG / SVG::GD
A second module (SVG::GD), written by Ronan Oger also provides similar functionality as
this module. Ronan and I are concurrently developing these modules with an eye towards
integrating them in the future. In principle, the primary difference is that GD::SVG aims
to generate SVG and SVG only. That is, it:
1. Does not store an internal representation of the GD image
2. Does not enable JPG, PNG, OR SVG output from a single pass
through data
3. Only occasioanally uses inherited methods from GD
Instead GD::SVG depends on the user to choose which output format they would like in
advance, "use"ing the appropriate module for that output. As described at the start of
this document, module selection between GD and GD::SVG can be made dynamically using eval
statements and variables for the differnet classes that GD and GD::SVG create.
There is a second reason for not maintaining a double representation of the data in GD and
SVG format: SVG documents can quickly become very large, especially with large datasets.
In cases where scripts are primarily generating png images in a server environment and
would only occasionally need to export SVG, gernerating an SVG image in parallel would
result in an unacceptable performance hit.
Thus GD::SVG aims to be a plugin for existing configurations that depend on GD but would
like to take advantage of SVG output.
SVG::GD, on the other hand, aims to tie in the raster-editing ability of GD with the power
of SVG output. In part, it aims to do this by inheriting many methods from GD directly and
bringing them into the functional space of GD. This makes SVG::GD easier to set up
initially (simply by adding the "use SVG::GD" below the "use GD" statement of your script.
GD::SVG sacrfices this initial ease-of-setup for more targeted applications.
ACKNOWLEDGEMENTS
Lincoln Stein, my postdoctoral mentor, author of GD.pm, and all around Perl stud. Ronan
Oger, author of SVG.pm conceptualized and implemented another wrapper around GD at about
the exact same time as this module. He also provided helpful discussions on implementing
GD functions into SVG. Oliver Drechsel and Marc Lohse provided patches to actually make
the stringUP method functional.
AUTHOR
Todd Harris, PhD <harris@cshl.org>
COPYRIGHT AND LICENSE
Copyright @ 2003-2005 Todd Harris and the Cold Spring Harbor Laboratory
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
SEE ALSO
GD, SVG, SVG::Manual, SVG::DOM