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

Friends,

I am learning about GD.pm and CGI programming and I tried this ... 
#!/usr/local/bin/perl -w
###
###
use strict;
use CGI;
use CGI::Carp qw /fatalsToBrowser/;

my $out = new CGI;


use GD;

# create a new image
my $im = new GD::Image(100,100);

# allocate some colors
my $white = $im->colorAllocate(255,255,255);
my $black = $im->colorAllocate(0,0,0);
my $red = $im->colorAllocate(255,0,0);
my $blue = $im->colorAllocate(0,0,255);

# make the background transparent and interlaced
$im->transparent($white);
$im->interlaced('true');

# Put a black frame around the picture
$im->rectangle(0,0,99,99,$black);

# Draw a blue oval
$im->arc(50,50,95,75,0,360,$blue);

# And fill it with red
$im->fill(50,50,$red);

#write to image.png
open( FH, '>image.png' ) or die "Can't image.png:$!\n";
# make sure we are writing to a binary stream
binmode FH;

# Convert the image to PNG and print it on standard output
print FH $im->png;
close FH;
print   $out->header( 'text/html' );
print <<HTML;
<html>
<head><title>GD test</title></head>
<body>
<img src='image.png'>
</body>
</html>
HTML

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When I run from the command line I get this ... 
~/cgi-bin/GD$ ./GDtest.pl
Content-Type: text/html; charset=ISO-8859-1

<html>
<head><title>GD test</title></head>
<body>
<img src='image.png'>
</body>
</html>

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But when I execute the CGI with my browser all I get is broken image?
Can anyone give me a pointer or two?
Thanks

Plankton: 1% Evil, 99% Hot Gas.

Replies are listed 'Best First'.
Re: GD newbee question
by matthewb (Curate) on Nov 02, 2003 at 06:45 UTC
    As Mr. Muskrat suggests, this is more to do with your appreciation of web server layout and permissions than Perl. If I run your script right here and then tail the error.log, I get: 
    [Sun Nov  2 06:36:56 2003] [error] [client 127.0.0.1] file permissions
+ deny server execution: /usr/lib/cgi-bin/image.png

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    If, however, I modify the open line to write a file in the document root and, in the HTML section, change the img src to look like this: 
    <img src="/image.png" alt="a red circle" />

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    ...I get a red circle, which I guess is what you are after.

    MB
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      Ah! Thanks!
      I changed these lines ... 
      open( FH, '>image.png' ) or die "Can't image.png:$!\n";
.
.
.
<img src='image.png'>

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      ... to ... 
      open( FH, '>../public_html/image.png' ) or die "Can't image.png:$!\n";
.
.
.
<img src='/image.png'>

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      ... and now it works! Thanks.

      Plankton: 1% Evil, 99% Hot Gas.
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Re: GD newbee question
by Mr. Muskrat (Canon) on Nov 02, 2003 at 04:46 UTC

    And the server log says what? And does the user that the web server runs as have access to write to this directory?

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