Mercio has asked for the wisdom of the Perl Monks concerning the following question:

I am having a problem with my code to return an image. My cgi file I am accessing looks like this 
#!c:/perl/bin/perl
print "Content-type: text/html\n\n"; 
print "<html><body><img src='test.cgi?asdf'></body></html>";

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and the test.cgi looks like this 
#!c:/perl/bin/perl

print "Content-type: image/gif\n\n";

open(IMG, "packplan.gif");
print <IMG>;
close(IMG);

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Now, instead of getting an image like I want when the first cgi script is accessed, i get an "X" like their was no image. What am I doing wrong?

Replies are listed 'Best First'.
Re: Image content help
by ambrus (Abbot) on Jun 17, 2004 at 06:54 UTC

    The second CGI is wrong. It reads only the first line of the image. You'll have to binmode the file., and read the whole, not just one line. (Update: /me was stupid here.)

    Update: also you'll have to chdir to the correct directory if you open the file with a relative path.

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      It reads only the first line of the image.

      This is not true. In the code line: 

      print <IMG>;

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      <IMG> is in list context. It should produce all the "lines" (by whatever definition of "line" $/ (the input record sepatator) gives - default separator is \n), then print should print all those elements joined by $, (the output field separator - by default undefined), followed by the content of $\ (the output record separator - also by default undefined).

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[d/l]
[select]
      I changed the second code to 
      #!c:/perl/bin/perl

print "Content-type: image/gif\n\n";

open(IMG, "packplan.gif");
binmode(IMG);
my @file = <IMG>;
close(IMG);
foreach my $line (@file){
    print $line;
}

      [download]
      still no go. This is my first time to try this image thing and I am lost. All the help you are giving me is appreciated.
[reply]
[d/l]
        You forgot to binmode STDOUT.

        MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
        I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
        ** The third rule of perl club is a statement of fact: pod is sexy.

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        Again, either use an absolute path in the open, or else chdir to the correct directory.

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Re: Image content help
by saskaqueer (Friar) on Jun 17, 2004 at 08:27 UTC

    The HTML page:

    #!perl -w
$| = 1;

use strict;
use CGI;

my $CGI = CGI->new();

print $CGI->header('text/html'), <<'END_HTML';
<html>

    <head>
        <title>Sample Image Page</title>
    </head>

    <body>
        <img src="test.cgi" />
    </body>

</html>
END_HTML

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    The perl script for the image (note that using read() is preferable compared to reading line-by-line when handling binary data such as images, as you may be pushing a lot of data into memory when you don't want to):

    #!perl -w
$| = 1;

use strict;
use CGI;

my $CGI = CGI->new();

print $CGI->header('image/gif');

open( my $img, '<', 'packplan.gif' )
    or die("open failed: $!");

binmode($img);
binmode(STDOUT);

while ( read($img, my $buf, 1024) ) {
    print $buf;
}

close($img) or die("close failed: $!");

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[d/l]
[select]
      Oh, I understand, so if you binmode(STDOUT) then it is binmoded for the rest of the script?
[reply]

        Correct.

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