to generate an image involving about a million calls to Imager->setpixel

... almost certainly indicates a design flaw. Unless, of course, your pixels arrive at random unpredictable coordinates, to be scattered over a megapixel (or larger) canvas. Which I suspect they don't. (And even then it should be setscanline for each pixel with packed color as arg). Doco (emphasis mine):

The getscanline() and setscanline() methods can work with pixels packed into scalars. This is useful to remove the cost of creating color objects, but should only be used when performance is an issue 
use strict;
use warnings;
use feature 'say';
use Time::HiRes 'time';
use Imager;

sub get_RGB_triplet { map { int rand 256 } 0 .. 2 }

{
    my $i = Imager-> new( xsize => 1000, ysize => 1000 );
    my $t = time;
    for my $y ( 0 .. 999 ) { 
        for my $x ( 0 .. 999 ) {
            my $c = Imager::Color-> new( get_RGB_triplet );
            $i-> setpixel( x => $x, y => $y, color => $c )
        }
    }
    say time - $t;
}
{
    my $i = Imager-> new( xsize => 1000, ysize => 1000 );
    my $t = time;
    for my $y ( 0 .. 999 ) { 
        my $packed_line = '';
        for my $x ( 0 .. 999 ) {
            $packed_line .= pack 'C3x', get_RGB_triplet;
        }
        $i-> setscanline( y => $y, pixels => $packed_line )
    }
    say time - $t;
}

__END__

5.78085088729858
0.599802017211914

[download]

In reply to Re: Double the speed of Imager->setpixel by Anonymous Monk
in thread Double the speed of Imager->setpixel by Anonymous Monk

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.