Perl Graphics Programming

Using Image::Magick

Image::Magick provides an all-purpose graphics API for Perl. You manipulate images by reading them into an Image::Magick object and then setting attributes and calling methods on that object. Most of the file formats supported by Image::Magick have certain attributes in common, though each may implement them differently. For example, JPEG and PNG both support compression, but have different compression schemes.

Image::Magick defines a wide range of file attributes, which are listed in tables later in this chapter. Many of the image manipulation functions (as well as Read( ) and Write( )) allow you to set various attributes when calling them, or you can use Set( ) to do it directly, as in:

$image->Set(loop=>100);
$image->[$x]->Set(dither=>1);

Note that you are not manipulating the image simply by setting attributes. In the above examples, setting the loop attribute adds a looping extension to a GIF file when it is written. The second example simply sets the default value of the dither attribute. Setting the attribute doesn’t dither the image, but subsequent operations, such as a call to Quantize( ), are performed using dithering.

Use Get( ) to get an attribute:

($w, $h, $d) = $q->Get('columns', 'rows', 'depth');
$colors = $q->[2]->Get('colors');

The functions GetAttribute( ) and SetAttribute( ) are aliases for Get( ) and Set( ) and may be used interchangeably.

Image::Magick provides a suite of methods for manipulating images. You can optionally add the word Image to ...