Another approach is to create your watermark on a transparent image of the same size (for simplicity) as the original. Ending with 2 images. Then you overlay those images using an appropriate blending mode which GD maybe has it built-in or create your own (warning: this example uses PHP's GD API which I am not sure is the same as that provided for Perl). To experiment with blending modes use gimp or photoshop if you own one and check layer modes

Another way similar to Fletch's is to sample a neighbourhood of original image's pixels around each of the watermark's non-transparent pixels. And pick the watermark pixel color (so no borders) to stand out using the color-wheel, there's a lot of theory about that and some simple equations to get "opposite" colors.

bw, bliako

In reply to Re: Adding a watermark to an image with GD::Image by bliako
in thread Adding a watermark to an image with GD::Image by Bod

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.