Use Tk::Photo to create a blank image and then the Canvas' createImage method to install it onto the Canvas. Once there, you can manipulate its pixels individually, like this: 
use Tk;

$mw = Tk::MainWindow->new;
$can = $mw->Canvas(-width => 320, -height => 240)->pack();
$img = $mw->Photo(-width => 320, -height => 240, -palette => '256/256/
+256');
$img->blank;
$can->createImage(0, 0, -image => $img, -anchor => 'nw');
$img->put(RED, -to => (160, 120));
printf "%6.6X", $img->get(160, 120);

MainLoop();

[download]
This code puts a red dot in the middle of a transparent image, then reads and outputs its color in hex. The documentation that covers this comes with the ActiveState distribution of Tk, but I'm sure you can find it on the web if you're not using that distro.

In reply to Re: Question about Tk Canvas, pixels, and images by Dr. Mu
in thread Question about Tk Canvas, pixels, and images by atcroft

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.