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