GD(3pm) User Contributed Perl Documentation GD(3pm)
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, 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, [$truecolor])
This works in exactly the same way as "newFromPng", but reads the
contents of an Windows BMP Bitmap file:
open (BMP,"coredump.bmp") || die;
$myImage = GD::Image->newFromWBMP(\*BMP) || die;
close BMP;
There is no newFromWBMPData() 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.
$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
perl v5.36.0 2022-10-19 GD(3pm)
Generated by dwww version 1.15 on Thu Jun 27 10:12:39 CEST 2024.