Perl Graphics Programming

Name

BlobToImage( ), ImageToBlob( )

Synopsis

$number_converted = $image->BlobToImage(blob_list)
@blobs = $image->ImageToBlob(attribute_list)

These methods allow you to convert images to and from Binary Large Objects (BLOBs). In Perl, a BLOB is simply a scalar that contains the image data in a particular file format. The BlobToImage( ) method takes one or more BLOBs and returns the number of BLOBs successfully converted to images. The ImageToBlob( ) method can take a list of Image::Magick attributes as parameters and returns an array of BLOBs, one for each image in the sequence.

The following code reads in a PNG file and prints the image as a JPEG on STDOUT:

#!/usr/bin/perl
use strict;
use Image::Magick;

my $img = new Image::Magick;

my $status = $img->Read('png:monkey.png');
my @blobs = $img->ImageToBlob(magick => 'jpeg');
print $blobs[0];

These methods can also be used to pass images between toolkits. The following code converts an Image::Magick image object into a GD image object, draws a rectangle using GD primitives, then converts the image back to Image::Magick:

#!/usr/bin/perl use strict; use Image::Magick; use GD; # First read an image with ImageMagick my $im = new Image::Magick; my $status = $im->Read('monkey.png'); if ($status) { die "$status!"; } # Convert to a blob and hand off to GD my @blobs = $im->ImageToBlob( ); my $gd = GD::Image->newFromPngData($blobs[0]); my $red = $gd->colorAllocate(255, 0, 0); # Outline in red $gd->rectangle(0, 0, (map {$_-1} $gd->getBounds), $red); ...