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<font face="Helvetica, Arial, sans-serif">Adding to what Matt just
said, once you've handled the issues he just explained, you'll be
needing sysopen(), sysseek(), sysread(), and syswrite(). Regular
Perl IO won't work for you.<br>
<br>
For image operations, I usually use the tried and true GD.pm<br>
<br>
Without understanding your reasons for eschewing the use of
modules in your work on this particular project (while respecting
your reasons all the same), I'd like to just make some generalized
points that a surprising many Perl users sadly do not know.
Please don't take it as an insult if you already know these
things, as I make the following statements for the benefit of the
group as a whole:<br>
<br>
While using modules is sometimes not an option-- for example you
may be working on something in a company with servers where you're
not allowed to install things-- it's no sign of weakness to take
advantage of everything Perl has to offer and try out a module.
Using the CPAN is a hallmark of a strong Perl programmer, in the
general opinion of the Perl community over the years. The
graphics modules we've discussed are written in C and are very
fast. You incur near zero penalty for using such libraries, which
are also optimized to work faster and more efficiently at their
specific tasks than what you'd be doing on your own. Unless you
have a very compelling reason to do otherwise, Perl and its
community always recommend not to reinvent the wheel when the
option is on the table to use its (very) nice CPAN wheels for
free. If it's a learning experience you seek, it's also of
benefit to look at the source code of these CPAN modules so you
can see how others are doing what you'd like to do on your own. I
always start looking at <a class="moz-txt-link-freetext" href="http://search.cpan.org">http://search.cpan.org</a><br>
<br>
Hope to see you at the meeting tomorrow night!<br>
<br>
--Tommy Butler<br>
<br>
On 01/08/2013 04:31 PM, Matthew Musgrove wrote:</font>
<blockquote
cite="mid:CAJaTdr2OOLufqCsu7h0nnfU1Nu_pibXASe0MMBKqRfhGOR0GkA@mail.gmail.com"
type="cite">
<div dir="ltr">
<p class=""><font face="Helvetica, Arial, sans-serif"><span
style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);">Jerry,</span></font></p>
<p class=""><font face="Helvetica, Arial, sans-serif"><span
style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);">You can’t just change a few bytes in an image
file and be done
with it. If you don’t want to use a module, then you’ll
need to be well
versed in the various image file formats before you can
ever start coding.
Otherwise you won’t know what bits to look for, much less
what values to use to
get the change you are interested in. </span></font></p>
<p class=""><font face="Helvetica, Arial, sans-serif"><span
style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);"> </span></font></p>
<p class=""><font face="Helvetica, Arial, sans-serif"><span
style="font-size: 11pt; font-family:
"Calibri","sans-serif"; color: rgb(31,
73, 125);">Matt</span></font></p>
</div>
<div class="gmail_extra"><font face="Helvetica, Arial, sans-serif"><br>
<br>
</font>
<div class="gmail_quote"><font face="Helvetica, Arial,
sans-serif">On Tue, Jan 8, 2013 at 4:16 PM, Jerry Kassebaum
<span dir="ltr"><<a moz-do-not-send="true"
href="mailto:kassebaumj@hotmail.com" target="_blank">kassebaumj@hotmail.com</a>></span>
wrote:<br>
</font>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
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<div>
<div><font face="Helvetica, Arial, sans-serif">How can
I use Perl to read a non-text file in hex, change
a few individual bytes, and write it back? Would
this work to change a gif or png, or would I have
to go down to binary?<br>
<br>
I appreciate the ImageMagic answer I received
before, and may have to resort to that, but I
would prefer to work with pure Perl without
loading a module. Surely there is a simple way to
read/write a file byte by byte?<span
class="HOEnZb"><font color="#888888"><br>
<div>
<p><span style="font-size: 10pt;
font-family:
"Tahoma","sans-serif";">
<br>
Jerry Kassebaum</span><font
face="Helvetica, Arial, sans-serif"><br>
</font></p>
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</font></span></font></div>
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</blockquote>
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