I want to process to detect edges without decompressing the image first.

You want to detect edges before you decompress the image? Are you sure? Most edge detection algorithms depends on having a matrix of pixels. That implies decompression. If you don't want to decompress all at once, you'll at least have to do some sort of banding algorithm to get an uncompressed band of scanlines, with enough scanlines to do incremental edge detection on. I've not heard of anyone having done this, but GIF decompression algorithm certainly makes this possible.

Unless you're under really tight space constraints, you'll get there a lot quicker if you decompress first.

In reply to Re: GIF Image Processing by dws
in thread GIF Image Processing by gri6507

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.