package GD;

# Copyright 1995 Lincoln D. Stein.  See accompanying README file for
# usage information

use strict;
require 5.004;
require FileHandle;
require Exporter;
require DynaLoader;
require AutoLoader;
use Carp 'croak','carp';

use GD::Image;
use GD::Polygon;

use vars qw($VERSION @ISA @EXPORT @EXPORT_OK %EXPORT_TAGS $AUTOLOAD);

$VERSION = '2.56';

@ISA = qw(Exporter DynaLoader);
# Items to export into callers namespace by default. Note: do not export
# names by default without a very good reason. Use EXPORT_OK instead.
# Do not simply export all your public functions/methods/constants.
@EXPORT = qw(
	gdBrushed
	gdDashSize
	gdMaxColors
	gdStyled
	gdStyledBrushed
	gdTiled
	gdTransparent
	gdAntiAliased
        gdArc
        gdChord
        gdPie
        gdNoFill
        gdEdged
	gdTinyFont
	gdSmallFont
	gdMediumBoldFont
	gdLargeFont
	gdGiantFont
	gdAlphaMax
	gdAlphaOpaque
	gdAlphaTransparent
);

@EXPORT_OK = qw (
	GD_CMP_IMAGE 
        GD_CMP_NUM_COLORS
	GD_CMP_COLOR
	GD_CMP_SIZE_X
	GD_CMP_SIZE_Y
        GD_CMP_TRANSPARENT
	GD_CMP_BACKGROUND
	GD_CMP_INTERLACE
	GD_CMP_TRUECOLOR
);

%EXPORT_TAGS = ('cmp'  => [qw(GD_CMP_IMAGE 
			      GD_CMP_NUM_COLORS
			      GD_CMP_COLOR
			      GD_CMP_SIZE_X
			      GD_CMP_SIZE_Y
			      GD_CMP_TRANSPARENT
			      GD_CMP_BACKGROUND
			      GD_CMP_INTERLACE
			      GD_CMP_TRUECOLOR
			     )
			  ]
	       );

# documentation error
*GD::Polygon::delete = \&GD::Polygon::deletePt;

sub AUTOLOAD {
    # This AUTOLOAD is used to 'autoload' constants from the constant()
    # XS function.  If a constant is not found then control is passed
    # to the AUTOLOAD in AutoLoader.

    my($constname);
    ($constname = $AUTOLOAD) =~ s/.*:://;
    my $val = constant($constname);
    if ($! != 0) {
	if ($! =~ /Invalid/) {
	    $AutoLoader::AUTOLOAD = $AUTOLOAD;
	    goto &AutoLoader::AUTOLOAD;
	}
	else {
	    my($pack,$file,$line) = caller;
	    die "Your vendor has not defined GD macro $pack\:\:$constname, used at $file line $line.\n";
	}
    }
    eval "sub $AUTOLOAD { $val }";
    goto &$AUTOLOAD;
}

bootstrap GD;


# Preloaded methods go here.
sub GD::gdSmallFont {
    return GD::Font->Small;
}

sub GD::gdLargeFont {
    return GD::Font->Large;
}

sub GD::gdMediumBoldFont {
    return GD::Font->MediumBold;
}

sub GD::gdTinyFont {
    return GD::Font->Tiny;
}

sub GD::gdGiantFont {
    return GD::Font->Giant;
}

sub GD::Image::startGroup { } # does nothing - used by GD::SVG
sub GD::Image::endGroup   { } # does nothing - used by GD::SVG
sub GD::Image::newGroup   {
    my $self = shift;
    GD::Group->new($self,$self->startGroup);
}

=head1 NAME

GD.pm - Interface to Gd Graphics Library

=head1 SYNOPSIS

    use GD;

    # create a new image
    $im = new GD::Image(100,100);

    # allocate some colors
    $white = $im->colorAllocate(255,255,255);
    $black = $im->colorAllocate(0,0,0);       
    $red = $im->colorAllocate(255,0,0);      
    $blue = $im->colorAllocate(0,0,255);

    # make the background transparent and interlaced
    $im->transparent($white);
    $im->interlaced('true');

    # Put a black frame around the picture
    $im->rectangle(0,0,99,99,$black);

    # Draw a blue oval
    $im->arc(50,50,95,75,0,360,$blue);

    # And fill it with red
    $im->fill(50,50,$red);

    # make sure we are writing to a binary stream
    binmode STDOUT;

    # Convert the image to PNG and print it on standard output
    print $im->png;

=head1 DESCRIPTION

B<GD.pm> is a Perl interface to Thomas Boutell's gd graphics library
(version 2.01 or higher; see below). GD allows you to create color
drawings using a large number of graphics primitives, and emit the
drawings as PNG files.

GD defines the following four classes:

=over 5


=item C<GD::Image>

An image class, which holds the image data and accepts graphic
primitive method calls.

=item C<GD::Font>

A font class, which holds static font information and used for text
rendering.

=item C<GD::Polygon>

A simple polygon object, used for storing lists of vertices prior to
rendering a polygon into an image.

=item C<GD::Simple>

A "simple" class that simplifies the GD::Image API and then adds a set
of object-oriented drawing methods using turtle graphics, simplified
font handling, ability to work in polar coordinates, HSV color spaces,
and human-readable color names like "lightblue". Please see
L<GD::Simple> for a description of these methods.

=back

A Simple Example:

	#!/usr/local/bin/perl

	use GD;

	# create a new image
	$im = new GD::Image(100,100);

	# allocate some colors
	$white = $im->colorAllocate(255,255,255);
	$black = $im->colorAllocate(0,0,0);       
	$red = $im->colorAllocate(255,0,0);      
	$blue = $im->colorAllocate(0,0,255);

	# make the background transparent and interlaced
	$im->transparent($white);
	$im->interlaced('true');

	# Put a black frame around the picture
	$im->rectangle(0,0,99,99,$black);

	# Draw a blue oval
	$im->arc(50,50,95,75,0,360,$blue);

	# And fill it with red
	$im->fill(50,50,$red);

	# make sure we are writing to a binary stream
	binmode STDOUT;

	# Convert the image to PNG and print it on standard output
	print $im->png;

Notes:

=over 5

=item 1.
To create a new, empty image, send a new() message to GD::Image, passing
it the width and height of the image you want to create.  An image
object will be returned.  Other class methods allow you to initialize
an image from a preexisting JPG, PNG, GD, GD2 or XBM file.

=item 2.
Next you will ordinarily add colors to the image's color table.
colors are added using a colorAllocate() method call.  The three
parameters in each call are the red, green and blue (rgb) triples for
the desired color.  The method returns the index of that color in the
image's color table.  You should store these indexes for later use.

=item 3.
Now you can do some drawing!  The various graphics primitives are
described below.  In this example, we do some text drawing, create an
oval, and create and draw a polygon.

=item 4.
Polygons are created with a new() message to GD::Polygon.  You can add
points to the returned polygon one at a time using the addPt() method.
The polygon can then be passed to an image for rendering.

=item 5.
When you're done drawing, you can convert the image into PNG format by
sending it a png() message.  It will return a (potentially large)
scalar value containing the binary data for the image.  Ordinarily you
will print it out at this point or write it to a file.  To ensure
portability to platforms that differentiate between text and binary
files, be sure to call C<binmode()> on the file you are writing
the image to.

=back

=head1 Object Constructors: Creating Images

The following class methods allow you to create new GD::Image objects.

=over 4

=item B<$image = GD::Image-E<gt>new([$width,$height],[$truecolor])>

=item B<$image = GD::Image-E<gt>new(*FILEHANDLE)>

=item B<$image = GD::Image-E<gt>new($filename)>

=item B<$image = GD::Image-E<gt>new($data)>

The new() method is the main constructor for the GD::Image class.
Called with two integer arguments, it creates a new blank image of the
specified width and height. For example:

	$myImage = new GD::Image(100,100) || die;

This will create an image that is 100 x 100 pixels wide.  If you don't
specify the dimensions, a default of 64 x 64 will be chosen.

The optional third argument, $truecolor, tells new() to create a
truecolor GD::Image object.  Truecolor images have 24 bits of color
data (eight bits each in the red, green and blue channels
respectively), allowing for precise photograph-quality color usage.
If not specified, the image will use an 8-bit palette for
compatibility with older versions of libgd.

Alternatively, you may create a GD::Image object based on an existing
image by providing an open filehandle, a filename, or the image data
itself.  The image formats automatically recognized and accepted are:
PNG, JPEG, XPM and GD2.  Other formats, including WBMP, and GD
version 1, cannot be recognized automatically at this time.

If something goes wrong (e.g. insufficient memory), this call will
return undef.

=item B<$image = GD::Image-E<gt>trueColor([0,1])>

For backwards compatibility with scripts previous versions of GD,
new images created from scratch (width, height) are palette based
by default.  To change this default to create true color images use:

	GD::Image->trueColor(1);

somewhere before creating new images.  To switch back to palette
based by default, use:

	GD::Image->trueColor(0);

=item B<$image = GD::Image-E<gt>newPalette([$width,$height])>

=item B<$image = GD::Image-E<gt>newTrueColor([$width,$height])>

The newPalette() and newTrueColor() methods can be used to explicitly
create an palette based or true color image regardless of the
current setting of trueColor().

=item B<$image = GD::Image-E<gt>newFromPng($file, [$truecolor])>

=item B<$image = GD::Image-E<gt>newFromPngData($data, [$truecolor])>

The newFromPng() method will create an image from a PNG file read in
through the provided filehandle or file path.  The filehandle must
previously have been opened on a valid PNG file or pipe.  If
successful, this call will return an initialized image which you can
then manipulate as you please.  If it fails, which usually happens if
the thing at the other end of the filehandle is not a valid PNG file,
the call returns undef.  Notice that the call doesn't automatically
close the filehandle for you.  But it does call C<binmode(FILEHANDLE)>
for you, on platforms where this matters.

You may use any of the following as the argument:

  1) a simple filehandle, such as STDIN
  2) a filehandle glob, such as *PNG
  3) a reference to a glob, such as \*PNG
  4) an IO::Handle object
  5) the pathname of a file

In the latter case, newFromPng() will attempt to open the file for you
and read the PNG information from it.

  Example1:

  open (PNG,"barnswallow.png") || die;
  $myImage = newFromPng GD::Image(\*PNG) || die;
  close PNG;

  Example2:
  $myImage = newFromPng GD::Image('barnswallow.png');

To get information about the size and color usage of the information,
you can call the image query methods described below. Images created
by reading PNG images will be truecolor if the image file itself is
truecolor. To force the image to be palette-based, pass a value of 0
in the optional $truecolor argument.

The newFromPngData() method will create a new GD::Image initialized
with the PNG format B<data> contained in C<$data>. 

=item B<$image = GD::Image-E<gt>newFromJpeg($file, [$truecolor])>

=item B<$image = GD::Image-E<gt>newFromJpegData($data, [$truecolor])>

These methods will create an image from a JPEG file.  They work just
like newFromPng() and newFromPngData(), and will accept the same
filehandle and pathname arguments.

Images created by reading JPEG images will always be truecolor.  To
force the image to be palette-based, pass a value of 0 in the optional
$truecolor argument.

=item B<$image = GD::Image-E<gt>newFromGif($file)>

=item B<$image = GD::Image-E<gt>newFromGifData($data)>

These methods will create an image from a GIF file.  They work just
like newFromPng() and newFromPngData(), and will accept the same
filehandle and pathname arguments.

Images created from GIFs are always 8-bit palette images. To convert
to truecolor, you must create a truecolor image and then perform a
copy.

=item B<$image = GD::Image-E<gt>newFromXbm($file)>

This works in exactly the same way as C<newFromPng>, but reads the
contents of an X Bitmap (black & white) file:

	open (XBM,"coredump.xbm") || die;
	$myImage = newFromXbm GD::Image(\*XBM) || die;
	close XBM;

There is no newFromXbmData() function, because there is no
corresponding function in the gd library.

=item B<$image = GD::Image-E<gt>newFromGd($file)>

=item B<$image = GD::Image-E<gt>newFromGdData($data)>

These methods initialize a GD::Image from a Gd file, filehandle, or
data.  Gd is Tom Boutell's disk-based storage format, intended for the
rare case when you need to read and write the image to disk quickly.
It's not intended for regular use, because, unlike PNG or JPEG, no
image compression is performed and these files can become B<BIG>.

	$myImage = newFromGd GD::Image("godzilla.gd") || die;
	close GDF;

=item B<$image = GD::Image-E<gt>newFromGd2($file)>

=item B<$image = GD::Image-E<gt>newFromGd2Data($data)>

This works in exactly the same way as C<newFromGd()> and
newFromGdData, but use the new compressed GD2 image format.

=item B<$image = GD::Image-E<gt>newFromGd2Part($file,srcX,srcY,width,height)>

This class method allows you to read in just a portion of a GD2 image
file.  In addition to a filehandle, it accepts the top-left corner and
dimensions (width,height) of the region of the image to read.  For
example:

	open (GDF,"godzilla.gd2") || die;
	$myImage = GD::Image->newFromGd2Part(\*GDF,10,20,100,100) || die;
	close GDF;

This reads a 100x100 square portion of the image starting from
position (10,20).

=item B<$image = GD::Image-E<gt>newFromXpm($filename)>

This creates a new GD::Image object starting from a B<filename>.  This
is unlike the other newFrom() functions because it does not take a
filehandle.  This difference comes from an inconsistency in the
underlying gd library.

	$myImage = newFromXpm GD::Image('earth.xpm') || die;

This function is only available if libgd was compiled with XPM
support.  

NOTE: The libgd library is unable to read certain XPM files, returning
an all-black image instead.

=head1 GD::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.

=head2 Image Data Output Methods

The following methods convert the internal drawing format into
standard output file formats.

=item B<$pngdata = $image-E<gt>png([$compression_level])>

This returns the image data in PNG format.  You can then print it,
pipe it to a display program, or write it to a file.  Example:

	$png_data = $myImage->png;
	open (DISPLAY,"| display -") || die;
	binmode DISPLAY;
	print DISPLAY $png_data;
	close DISPLAY;

Note the use of C<binmode()>.  This is crucial for portability to
DOSish platforms.

The optional $compression_level argument controls the amount of
compression to apply to the output PNG image.  Values range from 0-9,
where 0 means no compression (largest files, highest quality) and 9
means maximum compression (smallest files, worst quality).  A
compression level of -1 uses the default compression level selected
when zlib was compiled on your system, and is the same as calling
png() with no argument.  Be careful not to confuse this argument with
the jpeg() quality argument, which ranges from 0-100 and has the
opposite meaning from compression (higher numbers give higher
quality).

=item B<$gifdata = $image-E<gt>gifanimbegin([$GlobalCM [, $Loops]])>

For libgd version 2.0.33 and higher, this call begins an animated GIF
by returning the data that comprises animated gif image file header.
After you call this method, call gifanimadd() one or more times to add
the frames of the image. Then call gifanimend(). Each frame must be
the same width and height.

A typical sequence will look like this:

  my $gifdata = $image->gifanimbegin;
  $gifdata   .= $image->gifanimadd;    # first frame
  for (1..100) {
     # make a frame of right size
     my $frame  = GD::Image->new($image->getBounds);
     add_frame_data($frame);              # add the data for this frame
     $gifdata   .= $frame->gifanimadd;     # add frame
  }
  $gifdata   .= $image->gifanimend;   # finish the animated GIF
  print $gifdata;                     # write animated gif to STDOUT

If you do not wish to store the data in memory, you can print it to
stdout or a file.

The image that you call gifanimbegin on is used to set the image size,
color resolution and color map.  If argument $GlobalCM is 1, the image
color map becomes the GIF89a global color map.  If $Loops is given and
>= 0, the NETSCAPE2.0 application extension is created, with looping
count.  Looping count 0 means forever.

=item B<$gifdata = $image-E<gt>gifanimadd([$LocalCM [, $LeftOfs [, $TopOfs [, $Delay [, $Disposal [, $previm]]]]]])>

Returns the data that comprises one animated gif image frame.  You can
then print it, pipe it to a display program, or write it to a file.
With $LeftOfs and $TopOfs you can place this frame in different offset
than (0,0) inside the image screen.  Delay between the previous frame
and this frame is in 1/100s units.  Disposal is usually and by default
1.  Compression is activated by giving the previous image as a
parameter.  This function then compares the images and only writes the
changed pixels to the new frame in animation.  The Disposal parameter
for optimized animations must be set to 1, also for the first frame.
$LeftOfs and $TopOfs parameters are ignored for optimized frames.

=item B<$gifdata = $image-E<gt>gifanimend()>

Returns the data for end segment of animated gif file.  It always
returns string ';'.  This string must be printed to an animated gif
file after all image frames to properly terminate it according to GIF
file syntax.  Image object is not used at all in this method.

=item B<$jpegdata = $image-E<gt>jpeg([$quality])>

This returns the image data in JPEG format.  You can then print it,
pipe it to a display program, or write it to a file.  You may pass an
optional quality score to jpeg() in order to control the JPEG quality.
This should be an integer between 0 and 100.  Higher quality scores
give larger files and better image quality.  If you don't specify the
quality, jpeg() will choose a good default.

=item B<$gifdata = $image-E<gt>gif()>.

This returns the image data in GIF format.  You can then print it,
pipe it to a display program, or write it to a file.

=item B<$gddata = $image-E<gt>gd>

This returns the image data in GD format.  You can then print it,
pipe it to a display program, or write it to a file.  Example:

	binmode MYOUTFILE;
	print MYOUTFILE $myImage->gd;

=item B<$gd2data = $image-E<gt>gd2>

Same as gd(), except that it returns the data in compressed GD2
format.

=item B<$wbmpdata = $image-E<gt>wbmp([$foreground])>

This returns the image data in WBMP format, which is a black-and-white
image format.  Provide the index of the color to become the foreground
color.  All other pixels will be considered background.

=back

=head2 Color Control

These methods allow you to control and manipulate the GD::Image color
table.

=over 4

=item B<$index = $image-E<gt>colorAllocate(red,green,blue)>

This allocates a color with the specified red, green and blue
components and returns its index in the color table, if specified.
The first color allocated in this way becomes the image's background
color.  (255,255,255) is white (all pixels on).  (0,0,0) is black (all
pixels off).  (255,0,0) is fully saturated red.  (127,127,127) is 50%
gray.  You can find plenty of examples in /usr/X11/lib/X11/rgb.txt.

If no colors are allocated, then this function returns -1.

Example:

	$white = $myImage->colorAllocate(0,0,0); #background color
	$black = $myImage->colorAllocate(255,255,255);
	$peachpuff = $myImage->colorAllocate(255,218,185);

=item B<$index = $image-E<gt>colorAllocateAlpha(reg,green,blue,alpha)>

This allocates a color with the specified red, green, and blue components,
plus the specified alpha channel.  The alpha value may range from 0 (opaque)
to 127 (transparent).  The C<alphaBlending> function changes the way this
alpha channel affects the resulting image.

=item B<$image-E<gt>colorDeallocate(colorIndex)>

This marks the color at the specified index as being ripe for
reallocation.  The next time colorAllocate is used, this entry will be
replaced.  You can call this method several times to deallocate
multiple colors.  There's no function result from this call.

Example:

	$myImage->colorDeallocate($peachpuff);
	$peachy = $myImage->colorAllocate(255,210,185);

=item B<$index = $image-E<gt>colorClosest(red,green,blue)>

This returns the index of the color closest in the color table to the
red green and blue components specified.  If no colors have yet been
allocated, then this call returns -1.

Example:

	$apricot = $myImage->colorClosest(255,200,180);

=item B<$index = $image-E<gt>colorClosestHWB(red,green,blue)>

This also attempts to return the color closest in the color table to the
red green and blue components specified. It uses a Hue/White/Black 
color representation to make the selected color more likely to match
human perceptions of similar colors.

If no colors have yet been
allocated, then this call returns -1.

Example:

	$mostred = $myImage->colorClosestHWB(255,0,0);

=item B<$index = $image-E<gt>colorExact(red,green,blue)>

This returns the index of a color that exactly matches the specified
red green and blue components.  If such a color is not in the color
table, this call returns -1.

	$rosey = $myImage->colorExact(255,100,80);
	warn "Everything's coming up roses.\n" if $rosey >= 0;

=item B<$index = $image-E<gt>colorResolve(red,green,blue)>

This returns the index of a color that exactly matches the specified
red green and blue components.  If such a color is not in the color
table and there is room, then this method allocates the color in the
color table and returns its index.

	$rosey = $myImage->colorResolve(255,100,80);
	warn "Everything's coming up roses.\n" if $rosey >= 0;

=item B<$colorsTotal = $image-E<gt>colorsTotal> I<object method>

This returns the total number of colors allocated in the object.

	$maxColors = $myImage->colorsTotal;

In the case of a TrueColor image, this call will return undef.

=item B<$index = $image-E<gt>getPixel(x,y)> I<object method>

This returns the color table index underneath the specified
point.  It can be combined with rgb()
to obtain the rgb color underneath the pixel.

Example:

        $index = $myImage->getPixel(20,100);
        ($r,$g,$b) = $myImage->rgb($index);

=item B<($red,$green,$blue) = $image-E<gt>rgb($index)>

This returns a list containing the red, green and blue components of
the specified color index.

Example:

	@RGB = $myImage->rgb($peachy);

=item B<$image-E<gt>transparent($colorIndex)>

This marks the color at the specified index as being transparent.
Portions of the image drawn in this color will be invisible.  This is
useful for creating paintbrushes of odd shapes, as well as for
making PNG backgrounds transparent for displaying on the Web.  Only
one color can be transparent at any time. To disable transparency, 
specify -1 for the index.  

If you call this method without any parameters, it will return the
current index of the transparent color, or -1 if none.

Example:

	open(PNG,"test.png");
	$im = newFromPng GD::Image(PNG);
	$white = $im->colorClosest(255,255,255); # find white
	$im->transparent($white);
	binmode STDOUT;
	print $im->png;

=back

=head2 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.

=over 4

=item B<$image-E<gt>setBrush($image)>

You 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 B<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.

Example:

	# Create a brush at an angle
	$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

	# Set the brush
	$myImage->setBrush($diagonal_brush);
	
	# Draw a circle using the brush
	$myImage->arc(50,50,25,25,0,360,gdBrushed);

=item B<$image-E<gt>setThickness($thickness)>

Lines drawn with line(), rectangle(), arc(), and so forth are 1 pixel
thick by default.  Call setThickness() to change the line drawing
width.

=item B<$image-E<gt>setStyle(@colors)>

Styled lines consist of an arbitrary series of repeated colors and are
useful for generating dotted and dashed lines.  To create a styled
line, use setStyle() to specify a repeating series of colors.  It
accepts an array consisting of one or more color indexes.  Then draw
using the B<gdStyled> special color.  Another special color,
B<gdTransparent> can be used to introduce holes in the line, as the
example shows.

Example:

	# Set a style consisting of 4 pixels of yellow,
	# 4 pixels of blue, and a 2 pixel gap
	$myImage->setStyle($yellow,$yellow,$yellow,$yellow,
			   $blue,$blue,$blue,$blue,
			   gdTransparent,gdTransparent);
	$myImage->arc(50,50,25,25,0,360,gdStyled);

To combine the C<gdStyled> and C<gdBrushed> behaviors, you can specify
C<gdStyledBrushed>.  In this case, a pixel from the current brush
pattern is rendered wherever the color specified in setStyle() is
neither gdTransparent nor 0.

=item B<gdTiled>

Draw filled shapes and flood fills using a pattern.  The pattern is
just another image.  The image will be tiled multiple times in order
to fill the required space, creating wallpaper effects.  You must call
C<setTile> in order to define the particular tile pattern you'll use
for drawing when you specify the gdTiled color.
details.

=item B<gdStyled>

The gdStyled color is used for creating dashed and dotted lines.  A
styled line can contain any series of colors and is created using the
setStyled() command.

=item B<gdAntiAliased>

The C<gdAntiAliased> color is used for drawing lines with antialiasing
turned on.  Antialiasing will blend the jagged edges of lines with the
background, creating a smoother look.  The actual color drawn is set
with setAntiAliased().

=item B<$image-E<gt>setAntiAliased($color)>

"Antialiasing" is a process by which jagged edges associated with line
drawing can be reduced by blending the foreground color with an
appropriate percentage of the background, depending on how much of the
pixel in question is actually within the boundaries of the line being
drawn. All line-drawing methods, such as line() and polygon, will draw
antialiased lines if the special "color" B<gdAntiAliased> is used when
calling them.

setAntiAliased() is used to specify the actual foreground color to be
used when drawing antialiased lines. You may set any color to be the
foreground, however as of libgd version 2.0.12 an alpha channel
component is not supported.

Antialiased lines can be drawn on both truecolor and palette-based
images. However, attempts to draw antialiased lines on highly complex
palette-based backgrounds may not give satisfactory results, due to
the limited number of colors available in the palette. Antialiased
line-drawing on simple backgrounds should work well with palette-based
images; otherwise create or fetch a truecolor image instead. When
using palette-based images, be sure to allocate a broad spectrum of
colors in order to have sufficient colors for the antialiasing to use.

=item B<$image-E<gt>setAntiAliasedDontBlend($color,[$flag])>

Normally, when drawing lines with the special B<gdAntiAliased>
"color," blending with the background to reduce jagged edges is the
desired behavior. However, when it is desired that lines not be
blended with one particular color when it is encountered in the
background, the setAntiAliasedDontBlend() method can be used to
indicate the special color that the foreground should stand out more
clearly against.

Once turned on, you can turn this feature off by calling
setAntiAliasedDontBlend() with a second argument of 0:

 $image->setAntiAliasedDontBlend($color,0);

=back

=head2 Drawing Commands

These methods allow you to draw lines, rectangles, and ellipses, as
well as to perform various special operations like flood-fill.

=over 4

=item B<$image-E<gt>setPixel($x,$y,$color)>

This sets the pixel at (x,y) to the specified color index.  No value
is returned from this method.  The coordinate system starts at the
upper left at (0,0) and gets larger as you go down and to the right.
You can use a real color, or one of the special colors gdBrushed, 
gdStyled and gdStyledBrushed can be specified.

Example:

	# This assumes $peach already allocated
	$myImage->setPixel(50,50,$peach);

=item B<$image-E<gt>line($x1,$y1,$x2,$y2,$color)>

This draws a line from (x1,y1) to (x2,y2) of the specified color.  You
can use a real color, or one of the special colors gdBrushed, 
gdStyled and gdStyledBrushed.

Example:

	# Draw a diagonal line using the currently defined
	# paintbrush pattern.
	$myImage->line(0,0,150,150,gdBrushed);

=item B<$image-E<gt>dashedLine($x1,$y1,$x2,$y2,$color)>

DEPRECATED: The libgd library provides this method solely for backward
compatibility with libgd version 1.0, and there have been reports that
it no longer works as expected. Please use the setStyle() and gdStyled
methods as described below.

This draws a dashed line from (x1,y1) to (x2,y2) in the specified
color.  A more powerful way to generate arbitrary dashed and dotted
lines is to use the setStyle() method described below and to draw with
the special color gdStyled.

Example:

	$myImage->dashedLine(0,0,150,150,$blue);

=item B<$image-E<gt>rectangle($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.  Both real
color indexes and the special colors gdBrushed, gdStyled and
gdStyledBrushed are accepted.

Example:

	$myImage->rectangle(10,10,100,100,$rose);

=item B<$image-E<gt>filledRectangle($x1,$y1,$x2,$y2,$color)>

This draws a rectangle filed with the specified color.  You can use a
real color, or the special fill color gdTiled to fill the polygon
with a pattern.

Example:

	# read in a fill pattern and set it
	$tile = newFromPng GD::Image('happyface.png');
	$myImage->setTile($tile); 

	# draw the rectangle, filling it with the pattern
	$myImage->filledRectangle(10,10,150,200,gdTiled);

=item B<$image-E<gt>openPolygon($polygon,$color)>

This draws a polygon with the specified color.  The polygon must be
created first (see 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.

Example:

	$poly = new GD::Polygon;
	$poly->addPt(50,0);
	$poly->addPt(99,99);
	$poly->addPt(0,99);
	$myImage->openPolygon($poly,$blue);

=item B<$image-E<gt>unclosedPolygon($polygon,$color)>

This draws a sequence of connected lines with the specified color,
without connecting the first and last point to a closed polygon.  The
polygon must be created first (see below).  The polygon must have at
least three vertices.  Both real color indexes and the special colors
gdBrushed, gdStyled and gdStyledBrushed can be specified.

You need libgd 2.0.33 or higher to use this feature.

Example:

	$poly = new GD::Polygon;
	$poly->addPt(50,0);
	$poly->addPt(99,99);
	$poly->addPt(0,99);
	$myImage->unclosedPolygon($poly,$blue);

=item B<$image-E<gt>filledPolygon($poly,$color)>

This draws a polygon filled with the specified color.  You can use a
real color, or the special fill color gdTiled to fill the polygon
with a pattern.

Example:

	# 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
	$myImage->filledPolygon($poly,$peachpuff);

=item B<$image-E<gt>ellipse($cx,$cy,$width,$height,$color)>

=item B<$image-E<gt>filledEllipse($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.

=item B<$image-E<gt>arc($cx,$cy,$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.

You can specify a normal color or one of the special colors
B<gdBrushed>, B<gdStyled>, or B<gdStyledBrushed>.

Example:

	# draw a semicircle centered at 100,100
	$myImage->arc(100,100,50,50,0,180,$blue);

=item B<$image-E<gt>filledArc($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 mutually exclusive.  gdChord just connects the
starting and ending angles with a straight line, while gdArc produces
a rounded edge. gdPie is a synonym for gdArc. gdNoFill indicates 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."

Example:

  $image->filledArc(100,100,50,50,0,90,$blue,gdEdged|gdNoFill);

=item B<$image-E<gt>fill($x,$y,$color)>

This method flood-fills regions with the specified color.  The color
will spread through the image, starting at point (x,y), until it is
stopped by a pixel of a different color from the starting pixel (this
is similar to the "paintbucket" in many popular drawing toys).  You
can specify a normal color, or the special color gdTiled, to flood-fill
with patterns.

Example:

	# Draw a rectangle, and then make its interior blue
	$myImage->rectangle(10,10,100,100,$black);
	$myImage->fill(50,50,$blue);

=item B<$image-E<gt>fillToBorder($x,$y,$bordercolor,$color)>

Like C<fill>, this method flood-fills regions with the specified
color, starting at position (x,y).  However, instead of stopping when
it hits a pixel of a different color than the starting pixel, flooding
will only stop when it hits the color specified by bordercolor.  You
must specify a normal indexed color for the bordercolor.  However, you
are free to use the gdTiled color for the fill.

Example:

	# This has the same effect as the previous example
	$myImage->rectangle(10,10,100,100,$black);
	$myImage->fillToBorder(50,50,$black,$blue);

=back



=head2 Image Copying Commands

Two methods are provided for copying a rectangular region from one
image to another.  One method copies a region without resizing it.
The other allows you to stretch the region during the copy operation.

With either of these methods it is important to know that the routines
will attempt to flesh out the destination image's color table to match
the colors that are being copied from the source.  If the
destination's color table is already full, then the routines will
attempt to find the best match, with varying results.

=over 4

=item B<$image-E<gt>copy($sourceImage,$dstX,$dstY,>

B<				$srcX,$srcY,$width,$height)>

This is the simplest of the several copy operations, copying the
specified region from the source image to the destination image (the
one performing the method call).  (srcX,srcY) specify the upper left
corner of a rectangle in the source image, and (width,height) give the
width and height of the region to copy.  (dstX,dstY) control where in
the destination image to stamp the copy.  You can use the same image
for both the source and the destination, but the source and
destination regions must not overlap or strange things will happen.

Example:

	$myImage = new GD::Image(100,100);
	... various drawing stuff ...
	$srcImage = new GD::Image(50,50);
	... more drawing stuff ...
	# copy a 25x25 pixel region from $srcImage to
	# the rectangle starting at (10,10) in $myImage
	$myImage->copy($srcImage,10,10,0,0,25,25);

=item B<$image-E<gt>clone()>

Make a copy of the image and return it as a new object.  The new image
will look identical.  However, it may differ in the size of the color
palette and other nonessential details.

Example:

	$myImage = new GD::Image(100,100);
	... various drawing stuff ...
        $copy = $myImage->clone;

=item B<$image-E<gt>copyMerge($sourceImage,$dstX,$dstY,>

B<				$srcX,$srcY,$width,$height,$percent)>

This copies the indicated rectangle from the source image to the
destination image, merging the colors to the extent specified by
percent (an integer between 0 and 100).  Specifying 100% has the same
effect as copy() -- replacing the destination pixels with the source
image.  This is most useful for highlighting an area by merging in a
solid rectangle.

Example:

	$myImage = new GD::Image(100,100);
	... various drawing stuff ...
	$redImage = new GD::Image(50,50);
	... more drawing stuff ...
	# copy a 25x25 pixel region from $srcImage to
	# the rectangle starting at (10,10) in $myImage, merging 50%
	$myImage->copyMerge($srcImage,10,10,0,0,25,25,50);

=item B<$image-E<gt>copyMergeGray($sourceImage,$dstX,$dstY,>

B<				$srcX,$srcY,$width,$height,$percent)>

This is identical to copyMerge() except that it preserves the hue of
the source by converting all the pixels of the destination rectangle
to grayscale before merging.

=item B<$image-E<gt>copyResized($sourceImage,$dstX,$dstY,>

B<				$srcX,$srcY,$destW,$destH,$srcW,$srcH)>

This method is similar to copy() but allows you to choose different
sizes for the source and destination rectangles.  The source and
destination rectangle's are specified independently by (srcW,srcH) and
(destW,destH) respectively.  copyResized() will stretch or shrink the
image to accommodate the size requirements.

Example:

	$myImage = new GD::Image(100,100);
	... various drawing stuff ...
	$srcImage = new GD::Image(50,50);
	... more drawing stuff ...
	# copy a 25x25 pixel region from $srcImage to
	# a larger rectangle starting at (10,10) in $myImage
	$myImage->copyResized($srcImage,10,10,0,0,50,50,25,25);

=item B<$image-E<gt>copyResampled($sourceImage,$dstX,$dstY,>

B<				$srcX,$srcY,$destW,$destH,$srcW,$srcH)>

This method is similar to copyResized() but provides "smooth" copying
from a large image to a smaller one, using a weighted average of the
pixels of the source area rather than selecting one representative
pixel. This method is identical to copyResized() when the destination
image is a palette image.

=item B<$image-E<gt>copyRotated($sourceImage,$dstX,$dstY,>

B<				$srcX,$srcY,$width,$height,$angle)>

Like copyResized() but the $angle argument specifies an arbitrary
amount to rotate the image clockwise (in degrees).  In addition, $dstX
and $dstY species the B<center> of the destination image, and not the
top left corner.

=item B<$image-E<gt>trueColorToPalette([$dither], [$colors])>

This method converts a truecolor image to a palette image. The code for
this function was originally drawn from the Independent JPEG Group library
code, which is excellent. The code has been modified to preserve as much
alpha channel information as possible in the resulting palette, in addition
to preserving colors as well as possible. This does not work as well as
might be hoped. It is usually best to simply produce a truecolor
output image instead, which guarantees the highest output quality.
Both the dithering (0/1, default=0) and maximum number of colors used
(<=256, default = gdMaxColors) can be specified.

=back

=head2 Image Transformation Commands

Gd also provides some common image transformations:

=over 4

=item B<$image = $sourceImage-E<gt>copyRotate90()>

=item B<$image = $sourceImage-E<gt>copyRotate180()>

=item B<$image = $sourceImage-E<gt>copyRotate270()>

=item B<$image = $sourceImage-E<gt>copyFlipHorizontal()>

=item B<$image = $sourceImage-E<gt>copyFlipVertical()>

=item B<$image = $sourceImage-E<gt>copyTranspose()>

=item B<$image = $sourceImage-E<gt>copyReverseTranspose()>

These methods can be used to rotate, flip, or transpose an image.
The result of the method is a copy of the image.

=item B<$image-E<gt>rotate180()>

=item B<$image-E<gt>flipHorizontal()>

=item B<$image-E<gt>flipVertical()>

These methods are similar to the copy* versions, but instead
modify the image in place.

=back

=head2 Character and String Drawing

GD allows you to draw characters and strings, either in normal
horizontal orientation or rotated 90 degrees.  These routines use a
GD::Font object, described in more detail below.  There are four
built-in monospaced fonts, available in the global variables
B<gdGiantFont>, B<gdLargeFont>, B<gdMediumBoldFont>, B<gdSmallFont>
and B<gdTinyFont>.

In addition, you can use the load() method to load GD-formatted bitmap
font files at runtime. You can create these bitmap files from X11
BDF-format files using the bdf2gd.pl script, which should have been
installed with GD (see the bdf_scripts directory if it wasn't).  The
format happens to be identical to the old-style MSDOS bitmap ".fnt"
files, so you can use one of those directly if you happen to have one.

For writing proportional scaleable fonts, GD offers the stringFT()
method, which allows you to load and render any TrueType font on your
system.

=over 4

=item B<$image-E<gt>string($font,$x,$y,$string,$color)>

This method draws a string starting at position (x,y) in the specified
font and color.  Your choices of fonts are gdSmallFont, gdMediumBoldFont,
gdTinyFont, gdLargeFont and gdGiantFont.

Example:

	$myImage->string(gdSmallFont,2,10,"Peachy Keen",$peach);

=item B<$image-E<gt>stringUp($font,$x,$y,$string,$color)>

Just like the previous call, but draws the text rotated
counterclockwise 90 degrees.

=item B<$image-E<gt>char($font,$x,$y,$char,$color)>

=item B<$image-E<gt>charUp($font,$x,$y,$char,$color)>

These methods draw single characters at position (x,y) in the
specified 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.

=item $font = B<GD::Font-E<gt>load($fontfilepath)>

This method dynamically loads a font file, returning a font that you
can use in subsequent calls to drawing methods.  For example:

   my $courier = GD::Font->load('./courierR12.fnt') or die "Can't load font";
   $image->string($courier,2,10,"Peachy Keen",$peach);

Font files must be in GD binary format, as described above.

=item B<@bounds = $image-E<gt>stringFT($fgcolor,$fontname,$ptsize,$angle,$x,$y,$string)>

=item B<@bounds = GD::Image-E<gt>stringFT($fgcolor,$fontname,$ptsize,$angle,$x,$y,$string)>

=item B<@bounds = $image-E<gt>stringFT($fgcolor,$fontname,$ptsize,$angle,$x,$y,$string,\%options)>

This method uses TrueType to draw a scaled, antialiased string using
the TrueType vector font of your choice.  It requires that libgd to
have been compiled with TrueType support, and for the appropriate
TrueType font to be installed on your system.

The arguments are as follows:

  fgcolor    Color index to draw the string in
  fontname   A path to the TrueType (.ttf) font file or a font pattern.
  ptsize     The desired point size (may be fractional)
  angle      The rotation angle, in radians (positive values rotate counter clockwise)
  x,y        X and Y coordinates to start drawing the string
  string     The string itself

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)

In case of an error (such as the font not being available, or FT
support not being available), the method returns an empty list and
sets $@ to the error message.

The string may contain UTF-8 sequences like: "&#192;" 

You may also call this method from the GD::Image class name, in which
case it doesn't do any actual drawing, but returns the bounding box
using an inexpensive operation.  You can use this to perform layout
operations prior to drawing.

Using a negative color index will disable antialiasing, as described
in the libgd manual page at
L<http://www.boutell.com/gd/manual2.0.9.html#gdImageStringFT>.

An optional 8th argument allows you to pass a hashref of options to
stringFT().  Several hashkeys are recognized: B<linespacing>,
B<charmap>, B<resolution>, and B<kerning>. 

The value of B<linespacing> is supposed to be a multiple of the
character 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 B<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.

The value of B<resolution> is the vertical and horizontal resolution,
in DPI, in the format "hdpi,vdpi".  If present, the resolution will be
passed to the Freetype rendering engine as a hint to improve the
appearance of the rendered font.

The value of B<kerning> is a flag.  Set it to false to turn off the
default kerning of text.

Example:

 $gd->stringFT($black,'/dosc/windows/Fonts/pala.ttf',40,0,20,90,
              "hi there\r\nbye now",
	      {linespacing=>0.6,
	       charmap  => 'Unicode',
	      });

If GD was compiled with fontconfig support, and the fontconfig library
is available on your system, then you can use a font name pattern
instead of a path.  Patterns are described in L<fontconfig> and will
look something like this "Times:italic".  For backward
compatibility, this feature is disabled by default.  You must enable
it by calling useFontConfig(1) prior to the stringFT() call.

   $image->useFontConfig(1);

For backward compatibility with older versions of the FreeType
library, the alias stringTTF() is also recognized.

=item B<$hasfontconfig = $image-E<gt>useFontConfig($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.

This method can also be called as a class method of GD::Image;

=item B<$result = $image->stringFTCircle($cx,$cy,$radius,$textRadius,$fillPortion,$font,$points,$top,$bottom,$fgcolor)>

This draws text in a circle. Currently (libgd 2.0.33) this function
does not work for me, but the interface is provided for completeness.
The call signature is somewhat complex.  Here is an excerpt from the
libgd manual page:

Draws the text strings specified by top and bottom on the image, curved along
the edge of a circle of radius radius, with its center at cx and
cy. top is written clockwise along the top; bottom is written
counterclockwise along the bottom. textRadius determines the "height"
of each character; if textRadius is 1/2 of radius, characters extend
halfway from the edge to the center. fillPortion varies from 0 to 1.0,
with useful values from about 0.4 to 0.9, and determines how much of
the 180 degrees of arc assigned to each section of text is actually
occupied by text; 0.9 looks better than 1.0 which is rather
crowded. font is a freetype font; see gdImageStringFT. points is
passed to the freetype engine and has an effect on hinting; although
the size of the text is determined by radius, textRadius, and
fillPortion, you should pass a point size that "hints" appropriately
-- if you know the text will be large, pass a large point size such as
24.0 to get the best results. fgcolor can be any color, and may have
an alpha component, do blending, etc.

Returns a true value on success.

=back

=head2 Alpha channels

The alpha channel methods allow you to control the way drawings are
processed according to the alpha channel. When true color is turned
on, colors are encoded as four bytes, in which the last three bytes
are the RGB color values, and the first byte is the alpha channel.
Therefore the hexadecimal representation of a non transparent RGB
color will be: C=0x00(rr)(bb)(bb)

When alpha blending is turned on, you can use the first byte of the
color to control the transparency, meaning that a rectangle painted
with color 0x00(rr)(bb)(bb) will be opaque, and another one painted
with 0x7f(rr)(gg)(bb) will be transparent. The Alpha value must be >=
0 and <= 0x7f.

=over 4

=item B<$image-E<gt>alphaBlending($integer)>

The alphaBlending() method allows for two different modes of drawing
on truecolor images. In blending mode, which is on by default (libgd
2.0.2 and above), the alpha channel component of the color supplied to
all drawing functions, such as C<setPixel>, determines how much of the
underlying color should be allowed to shine through. As a result, GD
automatically blends the existing color at that point with the drawing
color, and stores the result in the image. The resulting pixel is
opaque. In non-blending mode, the drawing color is copied literally
with its alpha channel information, replacing the destination
pixel. Blending mode is not available when drawing on palette images.

Pass a value of 1 for blending mode, and 0 for non-blending mode.

=item B<$image-E<gt>saveAlpha($saveAlpha)>

By default, GD (libgd 2.0.2 and above) does not attempt to save full
alpha channel information (as opposed to single-color transparency)
when saving PNG images. (PNG is currently the only output format
supported by gd which can accommodate alpha channel information.) This
saves space in the output file. If you wish to create an image with
alpha channel information for use with tools that support it, call
C<saveAlpha(1)> to turn on saving of such information, and call
C<alphaBlending(0)> to turn off alpha blending within the library so
that alpha channel information is actually stored in the image rather
than being composited immediately at the time that drawing functions
are invoked.

=back


=head2 Miscellaneous Image Methods

These are various utility methods that are useful in some
circumstances.

=over 4

=item B<$image-E<gt>interlaced([$flag])>

This method sets or queries the image's interlaced setting.  Interlace
produces a cool venetian blinds effect on certain viewers.  Provide a
true parameter to set the interlace attribute.  Provide undef to
disable it.  Call the method without parameters to find out the
current setting.

=item B<($width,$height) = $image-E<gt>getBounds()>

This method will return a two-member list containing the width and
height of the image.  You query but not change the size of the
image once it's created.

=item B<$width = $image-E<gt>width>

=item B<$height = $image-E<gt>height>

Return the width and height of the image, respectively.

=item B<$is_truecolor = $image-E<gt>isTrueColor()>

This method will return a Boolean representing whether the image
is true color or not.

=item B<$flag = $image1-E<gt>compare($image2)>

Compare two images and return a bitmap describing the differences
found, if any.  The return value must be logically ANDed with one or
more constants in order to determine the differences.  The following
constants are available:

  GD_CMP_IMAGE             The two images look different
  GD_CMP_NUM_COLORS        The two images have different numbers of colors
  GD_CMP_COLOR             The two images' palettes differ
  GD_CMP_SIZE_X            The two images differ in the horizontal dimension
  GD_CMP_SIZE_Y            The two images differ in the vertical dimension
  GD_CMP_TRANSPARENT       The two images have different transparency
  GD_CMP_BACKGROUND        The two images have different background colors
  GD_CMP_INTERLACE         The two images differ in their interlace
  GD_CMP_TRUECOLOR         The two images are not both true color

The most important of these is GD_CMP_IMAGE, which will tell you
whether the two images will look different, ignoring differences in the
order of colors in the color palette and other invisible changes.  The
constants are not imported by default, but must be imported individually
or by importing the :cmp tag.  Example:

  use GD qw(:DEFAULT :cmp);
  # get $image1 from somewhere
  # get $image2 from somewhere
  if ($image1->compare($image2) & GD_CMP_IMAGE) {
     warn "images differ!";
  }

=item B<$image-E<gt>clip($x1,$y1,$x2,$y2)>

=item B<($x1,$y1,$x2,$y2) = $image-E<gt>clip>

Set or get the clipping rectangle.  When the clipping rectangle is
set, all drawing will be clipped to occur within this rectangle.  The
clipping rectangle is initially set to be equal to the boundaries of
the whole image. Change it by calling clip() with the coordinates of
the new clipping rectangle.  Calling clip() without any arguments will
return the current clipping rectangle.

=item B<$flag = $image-E<gt>boundsSafe($x,$y)>

The boundsSafe() method will return true if the point indicated by
($x,$y) is within the clipping rectangle, or false if it is not.  If
the clipping rectangle has not been set, then it will return true if
the point lies within the image boundaries.

=back

=head2 Grouping Methods

GD does not support grouping of objects, but GD::SVG does. In that
subclass, the following methods declare new groups of graphical
objects:

=over 4

=item $image->startGroup([$id,\%style])

=item $image->endGroup()

=item $group = $image->newGroup

See L<GD::SVG> for information.

=back

=head1 Polygons

A few primitive polygon creation and manipulation methods are
provided.  They aren't part of the Gd library, but I thought they
might be handy to have around (they're borrowed from my qd.pl
Quickdraw library).  Also see L<GD::Polyline>.

=over 3

=item B<$poly = GD::Polygon-E<gt>new>

Create an empty polygon with no vertices.

	$poly = new GD::Polygon;

=item B<$poly-E<gt>addPt($x,$y)>

Add point (x,y) to the polygon.

	$poly->addPt(0,0);
	$poly->addPt(0,50);
	$poly->addPt(25,25);
	$myImage->fillPoly($poly,$blue);

=item B<($x,$y) = $poly-E<gt>getPt($index)>

Retrieve the point at the specified vertex.

	($x,$y) = $poly->getPt(2);

=item B<$poly-E<gt>setPt($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);

=item B<($x,$y) = $poly-E<gt>deletePt($index)>

Delete the specified vertex, returning its value.

	($x,$y) = $poly->deletePt(1);


=item B<$poly-E<gt>clear()>

Delete all vertices, restoring the polygon to its initial empty state.

=item B<$poly-E<gt>toPt($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);
	$myImage->fillPoly($poly,$blue);

=item B<$vertex_count = $poly-E<gt>length>

Return the number of vertices in the polygon.

	$points = $poly->length;

=item B<@vertices = $poly-E<gt>vertices>

Return a list of all the vertices in the polygon object.  Each member
of the list is a reference to an (x,y) array.

	@vertices = $poly->vertices;
	foreach $v (@vertices)
	   print join(",",@$v),"\n";
	}

=item B<@rect = $poly-E<gt>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;

=item B<$poly-E<gt>offset($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.

	$poly->offset(10,30);

=item B<$poly-E<gt>map($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)
coordinates.  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);

=item B<$poly-E<gt>scale($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.

=item B<$poly-E<gt>transform($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.

=back

=head2 GD::Polyline

Please see L<GD::Polyline> for information on creating open polygons
and splines.

=head1 Font Utilities

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.

If you wish to add more built-in fonts, the directory bdf_scripts
contains two contributed utilities that may help you convert X-Windows
BDF-format fonts into the format that libgd uses internally.  However
these scripts were written for earlier versions of GD which included
its own mini-gd library.  These scripts will have to be adapted for
use with libgd, and the libgd library itself will have to be
recompiled and linked!  Please do not contact me for help with these
scripts: they are unsupported.

Each of these fonts is available both as an imported global
(e.g. B<gdSmallFont>) and as a package method
(e.g. B<GD::Font-E<gt>Small>).

=over 5

=item B<gdSmallFont>

=item B<GD::Font-E<gt>Small>

This is the basic small font, "borrowed" from a well known public
domain 6x12 font.

=item B<gdLargeFont>

=item B<GD::Font-E<gt>Large>

This is the basic large font, "borrowed" from a well known public
domain 8x16 font.

=item B<gdMediumBoldFont>

=item B<GD::Font-E<gt>MediumBold>

This is a bold font intermediate in size between the small and large
fonts, borrowed from a public domain 7x13 font;

=item B<gdTinyFont>

=item B<GD::Font-E<gt>Tiny>

This is a tiny, almost unreadable font, 5x8 pixels wide.

=item B<gdGiantFont>

=item B<GD::Font-E<gt>Giant>

This is a 9x15 bold font converted by Jan Pazdziora from a sans serif
X11 font.

=item B<$font-E<gt>nchars>

This returns the number of characters in the font.

	print "The large font contains ",gdLargeFont->nchars," characters\n";

=item B<$font-E<gt>offset>

This returns the ASCII value of the first character in the font

=item B<$width = $font-E<gt>width>

=item B<$height = $font-E<gt>height>

=item C<height>

These return the width and height of the font.

  ($w,$h) = (gdLargeFont->width,gdLargeFont->height);

=back

=head1 Obtaining the C-language version of gd

libgd, the C-language version of gd, can be obtained at URL
http://libgd.org/  Directions for installing and using it
can be found at that site.  Please do not contact me for help with
libgd.

=head1 AUTHOR

The GD.pm interface is copyright 1995-2010, Lincoln D. Stein. This
package and its accompanying libraries is free software; you can
redistribute it and/or modify it under the terms of the GPL (either
version 1, or at your option, any later version) or the Artistic
License 2.0.  Refer to LICENSE for the full license text.
package for details.

The latest versions of GD.pm are available at

  https://github.com/lstein/Perl-GD

=head1 SEE ALSO

L<GD::Polyline>,
L<GD::SVG>,
L<GD::Simple>,
L<Image::Magick>

=cut

1;

__END__