Provided by: libgd-perl_2.78-1build3_amd64 
NAME
GD.pm - Interface to Gd Graphics Library
SYNOPSIS
use GD;
# create a new image
$im = GD::Image->new(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;
DESCRIPTION
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:
"GD::Image"
An image class, which holds the image data and accepts graphic primitive method
calls.
"GD::Font"
A font class, which holds static font information and used for text rendering.
"GD::Polygon"
A simple polygon object, used for storing lists of vertices prior to rendering a
polygon into an image.
"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 GD::Simple for a description of these methods.
A Simple Example:
#!/usr/bin/perl
use GD;
# create a new image
$im = GD::Image->new(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:
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, XBM
or other supported image files.
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.
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.
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.
5. When you're done drawing, you can convert the image into PNG format by sending it a
png() message (or any other supported image format). 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 binmode() on the file you are
writing the image to.
Object Constructors: Creating Images
See GD::Image for the current list of supported Image formats.
The following class methods allow you to create new GD::Image objects.
$image = GD::Image->new([$width,$height],[$truecolor])
$image = GD::Image->new(*FILEHANDLE)
$image = GD::Image->new($filename)
$image = GD::Image->new($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 = GD::Image->new(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: GIF, PNG, JPEG, XBM, XPM, BMP, GD2, TIFF,
WEBP, HEIF or AVIF. 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.
$image = GD::Image->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);
before creating new images. To switch back to palette based by default, use:
GD::Image->trueColor(0);
$image = GD::Image->newPalette([$width,$height])
$image = GD::Image->newTrueColor([$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().
$image = GD::Image->newFromPng($file, [$truecolor])
$image = GD::Image->newFromPngData($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 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 = GD::Image->newFromPng(\*PNG) || die;
close PNG;
Example2:
$myImage = GD::Image->newFromPng('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 data contained in $data.
$image = GD::Image->newFromJpeg($file, [$truecolor])
$image = GD::Image->newFromJpegData($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.
$image = GD::Image->newFromGif($file, [$truecolor])
$image = GD::Image->newFromGifData($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.
$image = GD::Image->newFromXbm($file, [$truecolor])
This works in exactly the same way as "newFromPng", but reads the contents of an X
Bitmap (black & white) file:
open (XBM,"coredump.xbm") || die;
$myImage = GD::Image->newFromXbm(\*XBM) || die;
close XBM;
There is no newFromXbmData() function, because there is no corresponding function in
the gd library.
$image = GD::Image->newFromWBMP($file)
This works in exactly the same way as "newFromPng", but reads the contents of a
Wireless Application Protocol Bitmap (WBMP) file:
open (WBMP,"coredump.wbmp") || die;
$myImage = GD::Image->newFromWBMP(\*WBMP) || die;
close WBMP;
There is no newFromWBMPData() function, because there is no corresponding function in
the gd library.
$image = GD::Image->newFromBmp($file)
This works in exactly the same way as "newFromPng", but reads the contents of a
Windows Bitmap (BMP) file:
open (BMP,"coredump.bmp") || die;
$myImage = GD::Image->newFromBmp(\*BMP) || die;
close BMP;
There is no newFromBmpData() function, because there is no corresponding function in
the gd library.
$image = GD::Image->newFromGd($file)
$image = GD::Image->newFromGdData($data)
NOTE: GD and GD2 support was dropped witn libgd 2.3.2.
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 BIG.
$myImage = GD::Image->newFromGd("godzilla.gd") || die;
close GDF;
$image = GD::Image->newFromGd2($file)
$image = GD::Image->newFromGd2Data($data)
NOTE: GD and GD2 support was dropped witn libgd 2.3.2.
This works in exactly the same way as newFromGd() and newFromGdData, but use the new
compressed GD2 image format.
$image = GD::Image->newFromGd2Part($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).
$image = GD::Image->newFromXpm($filename)
This creates a new GD::Image object starting from a 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 = GD::Image->newFromXpm('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.
$bool = GD::supportsFileType($filename, $is_writing)
This returns a TRUE or FALSE value, if libgd supports reading or when the 2nd argument
is 1, if libgd supports writing the given filetype, depending on the filename
extension. Only with libgd versions >= gd-2.1.1.
Assuming LibGD is compiled with support for these image types, the following
extensions are supported:
.gif
.gd, .gd2
.wbmp
.bmp
.xbm
.tga
.png
.jpg, .jpeg
.tiff, .tif
.webp
.heic, .heix
.avif
.xpm
Filenames are parsed case-insensitively. .avifs is not yet suppurted upstream in
libavif.
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.
Image Data Output Methods
The following methods convert the internal drawing format into standard output file
formats.
$pngdata = $image->png([$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 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).
$gifdata = $image->gifanimbegin([$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.
$gifdata = $image->gifanimadd([$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.
$gifdata = $image->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.
$jpegdata = $image->jpeg([$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.
$gifdata = $image->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.
$gddata = $image->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;
$gd2data = $image->gd2
Same as gd(), except that it returns the data in compressed GD2 format.
$bmpdata = $image->bmp([$compression])
This returns the image data in BMP format, which is a Windows Bitmap. If compression
is set to 1, it will use RLE compression on the pixel data; otherwise, setting it to 0
(the default) will leave the BMP pixel data uncompressed.
$wbmpdata = $image->wbmp([$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.
$tiffdata = $image->tiff()
This returns the image data in TIFF format.
$webpdata = $image->webp([$quality])
This returns the image data in WEBP format, with the optional quality argument. The
default is 80, also chosen by the value -1. A quality value of >= 101 is considered
Lossless.
$webpdata = $image->heif([$quality])
This returns the truecolor image data in HEIF format, with the optional quality and
speed arguments. If truecolor is not set, this fails. The default quality is 80,
also chosen by the value -1. A quality value of 200 is considered Lossless.
$webpdata = $image->avif([$quality,$speed])
This returns the truecolor image data in AVIF format, with the AVif encoder and 444
chroma, and the optional quality argument. If truecolor is not set, this fails. The
default compression quality 1-100 is -1, the default speed 0-10 is 6.
$success = $image->_file($filename)
Writes an image to a file in the format indicated by the filename, with libgd versions
>= gd-2.1.1.
File type is determined by the extension of the file name. See "supportsFiletype" for
an overview of the parsing.
For file types that require extra arguments, "_file" attempts to use sane defaults:
C<gdImageGd2> chunk size = 0, compression is enabled.
C<gdImageJpeg> quality = -1 (i.e. the reasonable default)
C<gdImageWBMP> foreground is the darkest available color
C<gdImageWEBP> quality default
C<gdImageHEIF> quality default, codes = HEVC, chroma = 444
C<gdImageAVIF> quality default, speed = 6
Everything else is called with the two-argument function and so will use the default
values.
"_file" and the underlying libgd "gdImageFile" has some rudimentary error detection
and will return FALSE (0) if a detectable error occurred. However, the image loaders
do not normally return their error status so a result of TRUE (1) does **not** mean
the file was saved successfully.
Color Control
These methods allow you to control and manipulate the GD::Image color table for palette,
non-truecolor images.
$index = $image->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:
$black = $myImage->colorAllocate(0,0,0); #background color
$white = $myImage->colorAllocate(255,255,255);
$peachpuff = $myImage->colorAllocate(255,218,185);
$index = $image->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 "alphaBlending" function changes the way this alpha channel
affects the resulting image.
$image->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);
$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. If no colors have yet been allocated, then this call
returns -1.
Example:
$apricot = $myImage->colorClosest(255,200,180);
$index = $image->colorClosestAlpha(red,green,blue,alpha)
This returns the index of the color closest in the color table to the red green blue
and alpha components specified. If no colors have yet been allocated, then this call
returns -1.
Example:
$apricot = $myImage->colorClosestAlpha(255,200,180,0);
$index = $image->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);
$index = $image->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;
$index = $image->colorExactAlpha(red,green,blue,alpha)
This returns the index of a color that exactly matches the specified red green blue
and alpha components. If such a color is not in the color table, this call returns
-1.
$rosey = $myImage->colorExactAlpha(255,100,80,0);
warn "Everything's coming up roses.\n" if $rosey >= 0;
$index = $image->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;
$index = $image->colorResolveAlpha(red,green,blue,alpha)
This returns the index of a color that exactly matches the specified red green blue
and alpha 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->colorResolveAlpha(255,100,80,0);
warn "Everything's coming up roses.\n" if $rosey >= 0;
$colorsTotal = $image->colorsTotal 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.
$index = $image->getPixel(x,y) 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);
($red,$green,$blue) = $image->rgb($index)
This returns a list containing the red, green and blue components of the specified
color index.
Example:
@RGB = $myImage->rgb($peachy);
($alpha) = $image->alpha($index)
This returns an item containing the alpha component of the specified color index.
Example:
@RGB = $myImage->rgb($peachy);
$image->transparent($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 = GD::Image->newFromPng(PNG);
$white = $im->colorClosest(255,255,255); # find white
$im->transparent($white);
binmode STDOUT;
print $im->png;
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.
$image->setBrush($image)
You can draw lines and shapes using a brush pattern. Brushes are just palette, not
TrueColor, 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.
Example:
# Create a brush at an angle
$diagonal_brush = GD::Image->new(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);
$image->setThickness($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)
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 gdStyled special color. Another special color,
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 "gdStyled" and "gdBrushed" behaviors, you can specify
"gdStyledBrushed". In this case, a pixel from the current brush pattern is rendered
wherever the color specified in setStyle() is neither gdTransparent nor 0.
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 "setTile" in order to define the particular
tile pattern you'll use for drawing when you specify the gdTiled color. details.
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.
gdAntiAliased
The "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().
$image->setAntiAliased($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" 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.
$image->setAntiAliasedDontBlend($color,[$flag])
Normally, when drawing lines with the special 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);
Drawing Commands
These methods allow you to draw lines, rectangles, and ellipses, as well as to perform
various special operations like flood-fill.
$image->setPixel($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);
$image->line($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);
$image->dashedLine($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);
$image->rectangle($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. Both real color indexes and the special
colors gdBrushed, gdStyled and gdStyledBrushed are accepted.
Example:
$myImage->rectangle(10,10,100,100,$rose);
$image->filledRectangle($x1,$y1,$x2,$y2,$color) =item $image->setTile($otherimage)
This draws a rectangle 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:
# read in a fill pattern and set it
$tile = GD::Image->newFromPng('happyface.png');
$myImage->setTile($tile);
# draw the rectangle, filling it with the pattern
$myImage->filledRectangle(10,10,150,200,gdTiled);
$image->openPolygon($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 = GD::Polygon->new;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
$myImage->openPolygon($poly,$blue);
$image->unclosedPolygon($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 = GD::Polygon->new;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
$myImage->unclosedPolygon($poly,$blue);
$image->filledPolygon($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 = GD::Polygon->new;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
# draw the polygon, filling it with a color
$myImage->filledPolygon($poly,$peachpuff);
$image->ellipse($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.
$image->arc($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 right end 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 gdBrushed, gdStyled, or
gdStyledBrushed.
Example:
# draw a semicircle centered at 100,100
$myImage->arc(100,100,50,50,0,180,$blue);
$image->filledArc($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 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);
$image->fill($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);
$image->fillToBorder($x,$y,$bordercolor,$color)
Like "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);
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.
$image->copy($sourceImage,$dstX,$dstY,$srcX,$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 = GD::Image->new(100,100);
... various drawing stuff ...
$srcImage = GD::Image->new(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);
$image->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 = GD::Image->new(100,100);
... various drawing stuff ...
$copy = $myImage->clone;
$image->copyMerge($sourceImage,$dstX,$dstY,
$srcX,$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 = GD::Image->new(100,100);
... various drawing stuff ...
$redImage = GD::Image->new(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);
$image->copyMergeGray($sourceImage,$dstX,$dstY,
$srcX,$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.
$image->copyResized($sourceImage,$dstX,$dstY,
$srcX,$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 = GD::Image->new(100,100);
... various drawing stuff ...
$srcImage = GD::Image->new(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);
$image->copyResampled($sourceImage,$dstX,$dstY,
$srcX,$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.
$image->copyRotated($sourceImage,$dstX,$dstY,
$srcX,$srcY,$width,$height,$angle)
Like copyResized() but the $angle argument specifies an arbitrary amount to rotate the
image counter clockwise (in degrees). In addition, $dstX and $dstY species the center
of the destination image, and not the top left corner.
$image->trueColorToPalette([$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.
$image = $sourceImage->createPaletteFromTrueColor([$dither], [$colors])
Creates a new palette image from a truecolor image. Same as above, but returns a new
image.
Don't use these function -- write real truecolor PNGs and JPEGs. The disk space gain
of conversion to palette is not great (for small images it can be negative) and the
quality loss is ugly.
$error = $image->colorMatch($otherimage)
Bring the palette colors in $otherimage to be closer to truecolor $image. A negative
return value is a failure.
-1 image must be True Color
-2 otherimage must be indexed
-3 the images are meant to be the same dimensions
-4 At least 1 color in otherimage must be allocated
This method is only available with libgd >= 2.1.0
$image = $sourceImage->neuQuant($maxcolor=256,$samplefactor=5)
Creates a new palette image from a truecolor image.
samplefactor The quantization precision between 1 (highest quality) and 10
(fastest).
maxcolor The number of desired palette entries.
This is the same as createPaletteFromTrueColor with the quantization method
GD_QUANT_NEUQUANT. This does not support dithering. This method is only available
with libgd >= 2.1.0
Image Transformation Commands
Gd provides these simple image transformations, non-interpolated.
$image = $sourceImage->copyRotate90()
$image = $sourceImage->copyRotate180()
$image = $sourceImage->copyRotate270()
$image = $sourceImage->copyFlipHorizontal()
$image = $sourceImage->copyFlipVertical()
$image = $sourceImage->copyTranspose()
$image = $sourceImage->copyReverseTranspose()
These methods can be used to rotate, flip, or transpose an image. The result of the
method is a copy of the image.
$image->rotate180()
$image->flipHorizontal()
$image->flipVertical()
These methods are similar to the copy* versions, but instead modify the image in
place.
Image Interpolation Methods
Since libgd 2.1.0 there are better transformation methods, with these interpolation
methods:
GD_BELL - Bell
GD_BESSEL - Bessel
GD_BILINEAR_FIXED - fixed point bilinear
GD_BICUBIC - Bicubic
GD_BICUBIC_FIXED - fixed point bicubic integer
GD_BLACKMAN - Blackman
GD_BOX - Box
GD_BSPLINE - BSpline
GD_CATMULLROM - Catmullrom
GD_GAUSSIAN - Gaussian
GD_GENERALIZED_CUBIC - Generalized cubic
GD_HERMITE - Hermite
GD_HAMMING - Hamming
GD_HANNING - Hannig
GD_MITCHELL - Mitchell
GD_NEAREST_NEIGHBOUR - Nearest neighbour interpolation
GD_POWER - Power
GD_QUADRATIC - Quadratic
GD_SINC - Sinc
GD_TRIANGLE - Triangle
GD_WEIGHTED4 - 4 pixels weighted bilinear interpolation
GD_LINEAR - bilinear interpolation
$image->interpolationMethod( [$method] )
Gets or sets the interpolation methods for all subsequent interpolations. See above
for the valid values. Only available since libgd 2.2.0
$image->copyScaleInterpolated( width, height )
Returns a copy, using interpolation.
$image->copyRotateInterpolated( angle, bgcolor )
Returns a copy, using interpolation.
Image Filter Commands
Gd also provides some common image filters, they modify the image in place and return TRUE
if modified or FALSE if not. Most of them need libgd >= 2.1.0, with older versions those
functions are undefined.
$ok = $image->scatter($sub, $plus)
if $sub and $plus are 0, nothing is changed, TRUE is returned. if $sub >= $plus,
nothing is changed, FALSE is returned. else random pixels are changed.
$ok = $image->scatterColor($sub, $plus, @colors)
Similar to scatter, but using the given array of colors, i.e. palette indices.
$ok = $image->pixelate($blocksize, $mode)
if $blocksize <= 0, nothing is changed, FALSE is returned. if $blocksize == 1,
nothing is changed, TRUE is returned. else the following modes are observed:
GD_PIXELATE_UPPERLEFT
GD_PIXELATE_AVERAGE
$ok = $image->negate()
$ok = $image->grayscale()
$ok = $image->brightness($add)
$add: -255..255
$ok = $image->contrast($contrast)
$contrast: a double value. The contrast adjustment value. Negative values increase,
positive values decrease the contrast. The larger the absolute value, the stronger the
effect.
$ok = $image->color($red,$green,$blue,$alpha)
Change channel values of an image.
$red - The value to add to the red channel of all pixels.
$green - The value to add to the green channel of all pixels.
$blue - The value to add to the blue channel of all pixels.
$alpha - The value to add to the alpha channel of all pixels.
$ok = $image->selectiveBlur()
$ok = $image->edgeDetectQuick()
$ok = $image->gaussianBlur()
$ok = $image->emboss()
$ok = $image->meanRemoval()
$ok = $image->smooth($weight)
$image = $sourceImage->copyGaussianBlurred($radius, $sigma)
$radius: int, the blur radius (*not* diameter--range is 2*radius + 1) a radius, not a
diameter so a radius of 2 (for example) will blur across a region 5 pixels across (2
to the center, 1 for the center itself and another 2 to the other edge).
$sigma: the sigma value or a value <= 0.0 to use the computed default. represents the
"fatness" of the curve (lower == fatter).
The result is always truecolor.
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 gdGiantFont,
gdLargeFont, gdMediumBoldFont, gdSmallFont and 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 scalable fonts, GD offers the stringFT() method, which allows you
to load and render any TrueType font on your system.
$image->string($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);
$image->stringUp($font,$x,$y,$string,$color)
Just like the previous call, but draws the text rotated counterclockwise 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 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.
$font = GD::Font->load($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.
@bounds = $image->stringFT($fgcolor,$fontname,$ptsize,$angle,$x,$y,$string)
@bounds = GD::Image->stringFT($fgcolor,$fontname,$ptsize,$angle,$x,$y,$string)
@bounds = $image->stringFT($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 fontname argument is the name of the font, which can be a full pathname to a .ttf
file, or if not the paths in $ENV{GDFONTPATH} will be searched or if empty the libgd
compiled DEFAULT_FONTPATH. The TrueType extensions .ttf, .pfa, .pfb or .dfont can be
omitted.
The string may contain UTF-8 sequences like: "À"
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 <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: linespacing, charmap, resolution, and kerning.
The value of 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 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 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 kerning is a flag. Set it to false to turn off the default kerning of
text.
Example:
$gd->stringFT($black,'/c/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 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.
$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.
This method can also be called as a class method of GD::Image;
$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.
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.
$image->alphaBlending($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 "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.
$image->saveAlpha($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 saveAlpha(1) to
turn on saving of such information, and call 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.
Miscellaneous Image Methods
These are various utility methods that are useful in some circumstances.
$image->interlaced([$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.
($width,$height) = $image->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.
$width = $image->width
$height = $image->height
Return the width and height of the image, respectively.
$is_truecolor = $image->isTrueColor()
This method will return a Boolean representing whether the image is true color or not.
$flag = $image1->compare($image2)
Compare two images and return a bitmap describing the differences found, if any. The
return value must be logically AND'ed 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!";
}
$image->clip($x1,$y1,$x2,$y2)
($x1,$y1,$x2,$y2) = $image->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.
$flag = $image->boundsSafe($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.
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:
$image->startGroup([$id,\%style])
$image->endGroup()
$group = $image->newGroup
See GD::SVG for information.
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 GD::Polyline.
$poly = GD::Polygon->new
Create an empty polygon with no vertices.
$poly = GD::Polygon->new;
$poly->addPt($x,$y)
Add point (x,y) to the polygon.
$poly->addPt(0,0);
$poly->addPt(0,50);
$poly->addPt(25,25);
$myImage->fillPoly($poly,$blue);
($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->clear()
Delete all vertices, restoring the polygon to its initial empty state.
$poly->toPt($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);
$myImage->fillPoly($poly,$blue);
$vertex_count = $poly->length
Return the number of vertices in the polygon.
$points = $poly->length;
@vertices = $poly->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";
}
@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.
$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) 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);
$poly->scale($sx,$sy, [$tx,$ty])
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. Accepts an optional offset vector.
$poly->transform($sx,$rx,$ry,$sy, $tx,$ty)
Run each vertex of the polygon through a 2D affine 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.
libgd:
The transformation matrix is created using 6 numbers:
matrix[0] == xx
matrix[1] == yx
matrix[2] == xy
matrix[3] == xy (probably meaning yy here)
matrix[4] == x0
matrix[5] == y0
where the transformation of a given point (x,y) is given by:
x_new = xx * x + xy * y + x0;
y_new = yx * x + yy * y + y0;
GD::Polyline
Please see GD::Polyline for information on creating open polygons and splines.
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. gdSmallFont) and as a
package method (e.g. GD::Font->Small).
gdSmallFont
GD::Font->Small
This is the basic small font, "borrowed" from a well known public domain 6x12 font.
gdLargeFont
GD::Font->Large
This is the basic large font, "borrowed" from a well known public domain 8x16 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;
gdTinyFont
GD::Font->Tiny
This is a tiny, almost unreadable font, 5x8 pixels wide.
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";
$font->offset
This returns the ASCII value of the first character in the font
$width = $font->width
$height = $font->height
"height"
These return the width and height of the font.
($w,$h) = (gdLargeFont->width,gdLargeFont->height);
Helper Functions
GD::LIBGD_VERSION
Returns a number of the libgd VERSION, like 2.0204, 2.0033 or 2.01.
GD::VERSION_STRING
Returns the string of the libgd VERSION, like "2.2.4".
GD::constant
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.
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
SEE ALSO
GD::Polyline, GD::SVG, GD::Simple, Image::Magick