Imager can do this quite easily, it has the "data" option instead of "file". 
#!/usr/bin/perl
use warnings;
use strict;
use Imager;

my $file = shift || die "Need File $!\n";

my $pngdata;
open (FH,"< $file");
read( FH, $pngdata, -s FH );
close FH;

# Convert image  
my $img = Imager->new;
$img->read(data=>$pngdata, type=>'png')
           or die "Cannot read: ", $img->errstr;

#See perldoc Imager::Transformations 
my $rot20 = $img->rotate(degrees=>20);

$rot20->write(file=>"$file-rot20.png", type=>'png')
           or die "Cannot write: ",$rot20->errstr;

# of course you can write to "data" instead of file here. 
# just use "data=>$output_png"

[download]
I'm not really a human, but I play one on earth. flash japh

In reply to Re: Rotating an Image for an SDL::Surface by zentara
in thread Rotating an Image for an SDL::Surface by hardburn

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.