Introduction

PerlMagick is an objected-oriented Perl interface to GraphicsMagick. Use the module to read, manipulate, or write an image or image sequence from within a Perl script. This makes it very suitable for Web CGI scripts. You must have GraphicsMagick 1.0.0 or above and Perl version 5.005_02 or greater installed on your system for either of these utilities to work. There are a number of useful scripts available to show you the value of PerlMagick. The PerlMagick demo directory provides a number of sample demos.

Installation

cd PerlMagick
copy Makefile.nt Makefile.PL
perl Makefile.PL
nmake
nmake install

make test

cd demo
make

Overview

Any script that wants to use PerlMagick methods must first define the methods within its namespace and instantiate an image object. Do this with

use Graphics::Magick;
$image=Graphics::Magick->new;

Note that this differs from the ImageMagick version of PerlMagick which uses the namespace Image::Magick. Any PerlMagick code written for the ImageMagick version of PerlMagick requires a global substition of Image::Magick to Graphics::Magick in order to work with the GraphicsMagick version.

The new() method takes the same parameters as SetAttribute . For example:

$image=Graphics::Magick->new(size=>'384x256');

Next you will want to read an image or image sequence, manipulate it, and then display or write it. The input and output methods for PerlMagick are defined in Read or Write an Image. See Set an Image Attribute for methods that affect the way an image is read or written. Refer to Manipulate an Image for a list of methods to transform an image. Get an Image Attribute describes how to retrieve an attribute for an image. Refer to Create an Image Montage for details about tiling your images as thumbnails on a background. Finally, some methods do not neatly fit into any of the categories just mentioned. Review Miscellaneous Methods for a list of these methods.

Once you are finished with a PerlMagick object you should consider destroying it. Each image in an image sequence is stored in either virtual memory or as a file in the system's temporary file directory. This can potentially add up to megabytes of memory or disk. Upon destroying a PerlMagick object, the memory is returned for use by other Perl methods. The recommended way to destroy an object is with undef

undef $image;

To delete all the images but retain the Graphics::Magick object use

@$image = ();

and finally, to delete a single image from a multi-image sequence, use

undef $image->[x];

The next section illustrates how to use various PerlMagick methods to manipulate an image sequence.

Some of the PerlMagick methods require external programs such as Ghostscript. This may require an explicit path in your PATH environment variable to work properly. For example,

$ENV{PATH}='/bin:/usr/bin:/usr/local/bin';

Example Script

Here is an example script to get you started:

#!/usr/local/bin/perl
use Graphics::Magick;
my($image, $status);
$image = Graphics::Magick->new;
$status = $image->Read('girl.png', 'logo.png', 'rose.png');
warn "$status" if "$status";
$status = $image->Crop(geometry=>'100x100+100+100');
warn "$status" if "$status";
$status = $image->Write('x.gif');
warn "$status" if "$status";

The script reads three images, crops them, and writes a single image as a GIF animation sequence. In many cases you may want to access individual images of a sequence. The next example illustrates how this is done:

#!/usr/local/bin/perl
use Graphics::Magick;
my($image, $p, $q);
$image = new Graphics::Magick;
$image->Read('x1.png');
$image->Read('j*.jpg');
$image->Read('k.miff[1, 5, 3]');
$image->Contrast();
for ($x = 0; $image->[x]; $x++)
{
  $image->[x]->Frame('100x200') if $image->[x]->Get('magick') eq 'GIF';
  undef $image->[x] if $image->[x]->Get('columns') < 100;
}
$p = $image->[1];
$p->Draw(stroke=>'red', primitive=>'rectangle', points=>'20,20 100,100');
$q = $p->Montage();
undef $image;
$q->Write('x.miff');

Suppose you want to start out with a 100 by 100 pixel white canvas with a red pixel in the center. Try

$image = Graphics::Magick->new;
$image->Set(size=>'100x100');
$image->ReadImage('xc:white');
$image->Set('pixel[49,49]'=>'red');

Or suppose you want to convert your color image to grayscale:

$image->Quantize(colorspace=>'gray');

Here we annotate an image with a Taipai TrueType font:

$text = 'Works like magick!';
$image->Annotate(font=>'kai.ttf', pointsize=>40, fill=>'green', text=>$text);

Other clever things you can do with a PerlMagick objects include

$i = $#$p"+1"; # return the number of images associated with object p
push(@$q, @$p); # push the images from object p onto object q
@$p = (); # delete the images but not the object p
$p->Convolve([1, 2, 1, 2, 4, 2, 1, 2, 1]); # 3x3 Gaussian kernel

Read or Write an Image

Use the methods listed below to either read, write, or display an image or image sequence.

For convenience, methods Write(), Display(), and Animate() can take any parameter that SetAttribute knows about. For example,

$image->Write(filename=>'image.png', compression=>'None');

Use - as the filename to method Read() to read from standard in or to method Write() to write to standard out:

binmode STDOUT;
$image->Write('png:-');

To read an image from a disk file, use::

$image = Graphics::Magick->new; $filename = 'test.gif'; $status = $image->Read ($filename);

and to write the image back to the disk file, use:

$status = $image->Write($filename);

To read an image in the GIF format from a PERL filehandle, use:

$image = Graphics::Magick->new;
open(IMAGE, 'image.gif');
$status = $image->Read(file=>\*IMAGE);
close(IMAGE);

To write an image in the PNG format to a PERL filehandle, use:

$filename = "image.png";
open(IMAGE, ">$filename");
$status = $image->Write(file=>\*IMAGE, filename=>$filename);
close(IMAGE);

If %0Nd appears in the filename, it is interpreted as a printf format specification and the specification is replaced with the specified decimal encoding of the scene number. For example,

image%03d.miff

converts files image000.miff, image001.miff, etc.

You can optionally add Image to any method name. For example, ReadImage() is an alias for method Read().

Manipulate an Image

Once you create an image with, for example, method ReadImage() you may want to operate on it. Below is a list of all the image manipulations methods available to you with PerlMagick. There are examples of select PerlMagick methods. Here is an example call to an image manipulation method:

$image->Crop(geometry=>'100x100"+1"0+20');
$image->[x]->Frame("100x200");

Image method parameters are often redundant. For example, a 'geometry' string parameter (e.g. 800x600+10+20) is equivalent to the explicit use of width, height, x, and y, parameters.

The following image manipulation methods are available:

Note, that the geometry parameter is a short cut for the width and height parameters (e.g. geometry=>'106x80' is equivalent to width=>106, height=>80).

You can specify @filename in both Annotate() and Draw(). This reads the text or graphic primitive instructions from a file on disk. For example,

$image->Draw(fill=>'red', primitive=>'rectangle',
points=>'20,20 100,100 40,40 200,200 60,60 300,300');

Is equivalent to

$image->Draw(fill=>'red', primitive=>'@draw.txt');

Where draw.txt is a file on disk that contains this:

rectangle 20, 20 100, 100
rectangle 40, 40 200, 200
rectangle 60, 60 300, 300

The text parameter for methods, Annotate(), Comment(), Draw(), and Label() can include the image filename, type, width, height, or other image attribute by embedding these special format characters:

%b file size
%d comment
%d directory
%e filename extension
%f filename
%h height
%m magick
%p page number
%s scene number
%t top of filename
%w width
%x x resolution
%y y resolution
\n newline
\r carriage return

For example,

text=>"%m:%f %wx%h"

produces an annotation of MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480.

You can optionally add Image to any method name. For example, TrimImage() is an alias for method Trim().

Most of the attributes listed above have an analog in convert. See the documentation for a more detailed description of these attributes.

Set an Image Attribute

Use method Set() to set an image attribute. For example,

$image->Set(dither=>'True');
$image->[$x]->Set(delay=>3);

And here is a list of all the image attributes you can set:

Note, that the geometry parameter is a short cut for the width and height parameters (e.g. geometry=>'106x80' is equivalent to width=>106, height=> 80).

SetAttribute() is an alias for method Set().

Most of the attributes listed above have an analog in gm convert. See the gm documentation for a more detailed description of these attributes.

Get an Image Attribute

Use method Get() to get an image attribute. For example,

($a, $b, $c) = $image->Get('colorspace', 'magick', 'adjoin');
$width = $image->[3]->Get('columns');

In addition to all the attributes listed in Set an Image Attribute , you can get these additional attributes:

GetAttribute() is an alias for method Get().

Most of the attributes listed above have an analog in convert. See the documentation for a more detailed description of these attributes.

Create an Image Montage

Use method Montage() to create a composite image by combining several separate images. The images are tiled on the composite image with the name of the image optionally appearing just below the individual tile. For example,

$image->Montage(geometry=>'160x160', tile=>'2x2', texture=>'granite:');

And here is a list of Montage() parameters you can set:

Note, that the geometry parameter is a short cut for the width and height parameters (e.g. geometry=>'106x80' is equivalent to width=>106, height=> 80).

MontageImage() is an alias for method Montage().

Most of the attributes listed above have an analog in montage. See the documentation for a more detailed description of these attributes.

Working with Blobs

A blob contains data that directly represent a particular image format in memory instead of on disk. PerlMagick supports blobs in any of these image formats and provides methods to convert a blob to or from a particular image format.

ImageToBlob() returns the image data in their respective formats. You can then print it, save it to an ODBC database, write it to a file, or pipe it to a display program:

@blobs = $image->ImageToBlob();
open(DISPLAY,"| display -") || die;
binmode DISPLAY;
print DISPLAY $blobs[0];
close DISPLAY;

Method BlobToImage() returns an image or image sequence converted from the supplied blob:

@blob=$db->GetImage();
$image=Graphics::Magick->new(magick=>'jpg');
$image->BlobToImage(@blob);

Miscellaneous Methods

The Append() method append a set of images. For example,

$p = $image->Append(stack=>{true,false});

appends all the images associated with object $image. By default, images are stacked left-to-right. Set stack to True to stack them top-to-bottom.

The Average() method averages a set of images. For example,

$p = $image->Average();

averages all the images associated with object $image.

The Clone() method copies a set of images. For example,

$p = $image->Clone();

copies all the images from object $q to $p. You can use this method for single or multi-image sequences.

The Morph() method morphs a set of images. Both the image pixels and size are linearly interpolated to give the appearance of a meta-morphosis from one image to the next:

$p = $image->Morph(frames=>integer);

where frames is the number of in-between images to generate. The default is 1.

Mosaic() creates an mosaic from an image sequence.

Method Mogrify() is a single entry point for the image manipulation methods (Manipulate an Image). The parameters are the name of a method followed by any parameters the method may require. For example, these calls are equivalent:

$image->Crop('340x256+0+0');
$image->Mogrify('crop', '340x256+0+0');

Method MogrifyRegion() applies a transform to a region of the image. It is similar to Mogrify() but begins with the region geometry. For example, suppose you want to brighten a 100x100 region of your image at location (40, 50):

$image->MogrifyRegion('100x100+40+50', 'modulate', brightness=>50);

Ping() is a convenience method that returns information about an image without having to read the image into memory. It returns the width, height, file size in bytes, and the file format of the image. You can specify more than one filename but only one filehandle:

($width, $height, $size, $format) = $image->Ping('logo.png');
($width, $height, $size, $format) = $image->Ping(file=>\*IMAGE);
($width, $height, $size, $format) = $image->Ping(blob=>@blob);

This is a more efficient and less memory intensive way to query if an image exists and what its characteristics are.

To have full control over text positioning you need font metric information. Use

($x_ppem, $y_ppem, $ascender, $descender, $width, $height, $max_advance) =
$image->QueryFontMetrics(parameters);

Where parameters is any parameter of the Annotate method. The return values
are

* character width
* character height
* ascender
* descender
* text width
* text height
* maximum horizontal advance

Call QueryColor() with no parameters to return a list of known colors names or specify one or more color names to get these attributes: red, green, blue, and opacity value.

@colors = $image->QueryColor();
($red, $green, $blue, $opacity) = $image->QueryColor('cyan');
($red, $green, $blue, $opacity) = $image->QueryColor('#716bae');

QueryColorname() accepts a color value and returns its respective name or hex value;

$name = $image->QueryColorname('rgba(80,60,0,0)');

Call QueryFont() with no parameters to return a list of known fonts or specify one or more font names to get these attributes: font name, description, family, style, stretch, weight, encoding, foundry, format, metrics, and glyphs values.

@fonts = $image->QueryFont();
$weight = ($image->QueryFont('Helvetica'))[5];

Call QueryFormat() with no parameters to return a list of known image formats or specify one or more format names to get these attributes: adjoin, blob support, raw, decoder, encoder, description, and module.

@formats = $image->QueryFormat();
($adjoin, $blob_support, $raw, $decoder, $encoder, $description, $module) = $image->QueryFormat('gif');

Use RemoteCommand() to send a command to an already running display or animate application. The only parameter is the name of the image file to display or animate.

Finally, the Transform() method accepts a fully-qualified geometry specification for cropping or resizing one or more images. For example,

$p = $image->Transform(crop=>'100x100');

You can optionally add Image to any method name above. For example, PingImage() is an alias for method Ping().

Handling Errors

All PerlMagick methods return an undefined string context upon success. If any problems occur, the error is returned as a string with an embedded numeric status code. A status code less than 400 is a warning. This means that the operation did not complete but was recoverable to some degree. A numeric code greater or equal to 400 is an error and indicates the operation failed completely. Here is how errors are returned for the different methods:

• Methods which return a number (e.g. Read(), Write()):

  $status = $image->Read(...);
  warn "$status" if "$status"; # print the error message
  $status =~ /(\d+)/;
  print $1; # print the error number
  print 0+$status; # print the number of images read
  

• Methods which operate on an image (e.g. Resize(), Crop()):

  $status = $image->Crop(...);
  warn "$status" if "$status"; # print the error message
  $status =~ /(\d+)/;
  print $1; # print the error number
  

• Methods which return images (Average(), Montage(), Clone()) should be checked for errors this way:

  $status = $image->Montage(...);
  warn "$status" if !ref($status); # print the error message
  $status =~ /(\d+)/;
  print $1; # print the error number
  

Here is an example error message:

Error 400: Memory allocation failed

Below is a list of error and warning codes:

The following illustrates how you can use a numeric status code:

$status = $image->Read('rose.png');
$status =~ /(\d+)/;
die "unable to continue" if ($1 == ResourceLimitError);

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