Resizing an image with perl.

DigitalKitty has asked for the wisdom of the Perl Monks concerning the following question:

Hi all.

This has been a *very* stressful week. So to entertain myself I was thinking about creating a perl program that would enable one to create a banner ( or poster ) based on an image you already had ( or could make ). Here it is:


#!/usr/bin/perl -w

use strict;
use GD;

my $order_of_mag;
print "Enter order of magnitude for new picture: ";
chomp( $order_of_mag = <STDIN> );

my $pic = GD::Image->newFromPng( "pc.png" );
my @size = $pic->getBounds();
my @newSize = map( { $_ * $order_of_mag } @size );

my $newPic = new GD::Image ( @newSize );
$newPic->copyResized( $pic, 0, 0, 0, 0, @newSize, @size );

open FH, ">pc2.png" || die "Could not write to file: $!\n";

binmode FH;
print FH $newPic->png();

close FH or die "Could not close file: $!\n"
[download]

If you set the order of magnitude quite high, simply click on the little orange box that appears ( in IE ) then scroll back and forth. Since it writes the new image to a different file, the original won't be disturbed.
Any suggestions on how to improve it are most welcome.

Thanks,
-Katie.

Comment on Resizing an image with perl. Download Code

Replies are listed 'Best First'.
Re: Resizing an image with perl. by io (Scribe) on Aug 12, 2002 at 16:33 UTC
This line may be a problem: `open FH, ">pc2.png" \|\| die "Could not write to file: $!\n";` [download] As the '`\|\|`' operator has a high predence, perl will try to compare the string `">pc2.png"` instead of the return value of the open statement. You us the '`or`' operator instead, or use brackets like `open (FH, ">pc2.png") \|\| die`. But the rest of your code looks fine, using strict and warnings and such :-)	[reply] [d/l] [select]
Re: Resizing an image with perl. by seattlejohn (Deacon) on Aug 12, 2002 at 17:29 UTC
Nitpick: You're misusing the term "order of magnitude". An order of magnitude is a 10x difference, two orders of magnitude is a 100x difference, and so on. To perform as advertised, your `map` should really look something like this: `map {$_ * 10**$order_of_magnitude} @size;` But I suspect that's not what you intended, and the term you meant to use was something like "factor".	[reply] [d/l]
Re: Resizing an image with perl. by hossman (Prior) on Aug 13, 2002 at 00:59 UTC
You probably want to consider using Image::Magick for this, since GD has issues with more then 256 color images UPDATE: GD 2.00 was released just 3 days prior to this post, and reportedly fixes the 256 color issues. UPDATE#2 while making update#1, i just realized i had linked to the completely wrong node about GD. I've fixed the link.	[reply]
Re: Re: Resizing an image with perl. by xtype (Deacon) on Aug 15, 2002 at 08:29 UTC
I am happy to say, that is not true. I think that you need to read: http://www.boutell.com/gd/manual2.0.1.html "...version 2.0 does include ... both truecolor and palette images, resampling (smooth resizing of truecolor images) and so forth. " After you have updating your gd library you should go and visit Lincoln Stein's space on cpan to download GD-2.01. http://search.cpan.org/author/LDS/ I had been using GD-2.00 since the 6th with decent results and was very pleased to see GD-2.01 made available. Thanks Lincoln! An excellent module. Mmmm... 16,777,216 colors for me. ImageMagick is huge and slow. I was using shell tools (djpeg, etc) simply to avoid it.	[reply]