PerlMagick, Perl API

In this example, we compare the ImageMagick logo to a sharpened reconstruction:

use Image::Magick;

$logo=Image::Magick->New();
$logo->Read('logo:');
$sharp=Image::Magick->New();
$sharp->Read('logo:');
$sharp->Sharpen('0x1');
$difference=$logo->Compare(image=>$sharp, metric=>'rmse');
print $difference->Get('error'), "\n";
$difference->Display();

In addition to the reported root mean squared error of around 0.024, a difference image is displayed so you can visually identify the difference between the images.

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

Direct-access to Image Pixels

Use these methods to obtain direct access to the image pixels:

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

$q = $p->Clone();

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

Coalesce() composites a set of images while respecting any page offsets and disposal methods. GIF, MIFF, and MNG animation sequences typically start with an image background and each subsequent image varies in size and offset. A new image sequence is returned with all images the same size as the first images virtual canvas and composited with the next image in the sequence.. For example,

$q = $p->Coalesce();

The ComplexImages() method performs complex mathematics on an image sequence. For example,

$p = $image->ComplexImages('conjugate');

The EvaluateImages() method applies an arithmetic, logical or relational expression to a set of images. For example,

$p = $image->EvaluateImages('mean');

averages all the images associated with object $image.

The Features() method returns features for each channel in the image in each of four directions (horizontal, vertical, left and right diagonals) for the specified distance. The features include the angular second momentum, contrast, correlation, sum of squares: variance, inverse difference moment, sum average, sum variance, sum entropy, entropy, difference variance, difference entropy, information measures of correlation 1, information measures of correlation 2, and maximum correlation coefficient. Values in RGB, CMYK, RGBA, or CMYKA order (depending on the image type).

@features = $image->Features(1);

The Flatten() method flattens a set of images and returns it. For example,

$p = $images->Flatten(background=>'none');
$p->Write('flatten.png');

The sequence of images is replaced by a single image created by composing each image after the first over the first image.

The Fx() method applies a mathematical expression to a set of images and returns the results. For example,

$p = $image->Fx(expression=>'(g+b)/2.0',channel=>'red');
$p->Write('fx.miff');

replaces the red channel with the average of the green and blue channels.

See FX, The Special Effects Image Operator for a detailed discussion of this method.

Histogram() returns the unique colors in the image and a count for each one. The returned values are an array of red, green, blue, opacity, and count values.

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);

PerceptualHash() maps visually identical images to the same or similar hash-- useful in image retrieval, authentication, indexing, or copy detection as well as digital watermarking. For each channel and for the sRGB and the HCLp colorspaces, 7 hash values are returned For an sRGB images, for example, expect 42 perceptual hashes.

@phash = $image->PerceptualHash();

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

Poly() builds a polynomial from the image sequence and the corresponding terms (coefficients and degree pairs):

$p = $image->Poly([0.5,1.0,0.25,2.0,1.0,1.0]);

PreviewImage() tiles 9 thumbnails of the specified image with an image processing operation applied at varying strengths. This may be helpful pin-pointing an appropriate parameter for a particular image processing operation. Choose from these operations: Rotate, Shear, Roll, Hue, Saturation, Brightness, Gamma, Spiff, Dull, Grayscale, Quantize, Despeckle, ReduceNoise, AddNoise, Sharpen, Blur, Threshold, EdgeDetect, Spread, Solarize, Shade, Raise, Segment, Swirl, Implode, Wave, OilPaint, CharcoalDrawing, JPEG. Here is an example:

$preview = $image->Preview('Gamma');
$preview->Display();

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:

1. character width
2. character height
3. ascender
4. descender
5. text width
6. text height
7. maximum horizontal advance
8. bounds: x1
9. bounds: y1
10. bounds: x2
11. bounds: y2
12. origin: x
13. origin: y

Use QueryMultilineFontMetrics() to get the maximum text width and height for multiple lines of text.

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) = $image->QueryColor('cyan');
($red, $green, $blue, $alpha) = $image->QueryColor('#716baeff');

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');

Call MagickToMime() with the image format name to get its MIME type such as image/tiff from tif.

$mime = $image->MagickToMime('tif');

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.

$image->RemoteCommand('image.jpg');

The Smush() method smushes a set of images together. For example,

$p = $image->Smush(stack=>{true,false},offset=>integer);

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

Statistics() returns the image statistics for each channel in the image. The returned values are an array of depth, minima, maxima, mean, standard deviation, kurtosis, skewness, and entropy values in RGB, CMYK, RGBA, or CMYKA order (depending on the image type).

@statistics = $image->Statistics();

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+0+0');

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

Handling Exceptions

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 exceptions are returned for the different methods:

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

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

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

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

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

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

Here is an example error message:

Error 400: Memory allocation failed

Review the complete list of error and warning codes.

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

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

Constants

PerlMagick includes these constants:

BlobError
BlobWarning
CacheError
CacheWarning
CoderError
CoderWarning
ConfigureError
ConfigureWarning
CorruptImageError
CorruptImageWarning
DelegateError
DelegateWarning
DrawError
DrawWarning
ErrorException
FatalErrorException
FileOpenError
FileOpenWarning
ImageError
ImageWarning
MissingDelegateError
MissingDelegateWarning
ModuleError
ModuleWarning
Opaque
OptionError
OptionWarning
QuantumDepth
QuantumRange
RegistryError
RegistryWarning
ResourceLimitError
ResourceLimitWarning
StreamError
StreamWarning
Success
Transparent
TypeError
TypeWarning
WarningException
XServerError
XServerWarning

You can access them like this:

Image::Magick->QuantumDepth