Thanks a lot for your thoughts, and I'm glad you liked the question :). The speed as it is now, maybe up to 5 sec per image, is _quite_ OK. So much time, because application scans 4 narrow edges of large image (to be 100% sure), in both directions (orientations), i.e. 8 partial scans per image, -- very easy to do with PDL slicing and "get_dataref" -- they do all rotation and cropping. Text is, indeed, simple, but its size, position, etc. are unknown.

Spending time on PDL source (for which I'm not qualified enough, anyway), will be an overkill. It was just that, BEFORE knowing why it was so slow, I was a little frustrated that 2 workers (no more, because they also do some other stuff and can consume lots of memory) i.e. threads (max_workers being set to 2 for my descendant of IO::Async::Function, in IO::Async application), each one processing just a single file, blocked the whole queue for _more than 40 minutes_. But, now it is OK.

In reply to Re^10: Why this code is so slow if run in thread? by vr
in thread Why this code is so slow if run in thread? by vr

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.