Provided by: libgd-svg-perl_0.33-3_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
perl v5.30.3 2020-07-29 SVG(3pm)