GD malformed header error

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

I had GD installed on the server(FreeBSD) and haven't been able to get a script to run yet. Here's a piece of code the ISP offered, but even they can't run it.

#!/usr/local/bin/perl
use GD;
Context: "text/html\n\n";
# create a new image
$im = new GD::Image(100,100);

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

# make sure we are writing to a binary stream
    binmode STDOUT;

# Convert the image to PNG and print it on standard output
    print $im->png;
[download]

Here's the error it produces in my error log.

Thu Apr 4 06:23:58 2002 access to /cgi-bin/gdtrial.pl failed for XX.XXX.XXX.XX, reason: malformed header from script. Bad header=‰PNG

I've also tried GD:Graph with this code:

#!/usr/bin/perl 
 
  use strict;
  use GD::Graph::bars;

  my @data = (
  ["Jan-01","Feb-01","Mar-01", "Apr-01","May-01","Jun-01","Jul-01","Au
+g-01","Sep-01"],
  [21,25,33,39,49,48,40,45,15]
          );

  my $graph = new GD::Graph::bars;

  $graph->set(
      x_label         => 'Month',
      y_label         => 'Revenue ($1,000s)',
      title           => 'Monthly Online Sales for 2001',
      bar_spacing     => 10
  )
  or warn $graph->error;

  $graph->plot(\@data) or die $graph->error;

  open(GRAPH,">graph1.jpg") || die "Cannot open graph1.jpg: $!\n";
  print GRAPH $graph->gd->jpeg(100);
[download]

It produces the same type of error. I CPAN'd GD:Graph and it says it's up to date. What am I doing wrong? Has anyone come across a problem like this?

TIA

peppiv

Comment on GD malformed header error Select or Download Code

Replies are listed 'Best First'.
Re: GD malformed header error by projekt21 (Friar) on Apr 04, 2002 at 14:08 UTC
When running a CGI you need to output (print) what the browser shall see. Normally this is HTML-Code, but plain text or images are fine, too. First of all you need to print a header containing the content-type and two newlines: `print "Content-type: image/png\n\n"` [download] ... and remove that line saying: Context: .... This should work for a trial. I would further encourage you to `use strict;`, enable warnings (-w) AND `use CGI;`. `#!/usr/bin/perl -w use strict; use CGI; my $q = CGI->new; print $q->header("image/png"); ## later print $im->png;` [download] I'm sure, GD is not to blame. alex pleiner <alex@zeitform.de> zeitform Internet Dienste	[reply] [d/l] [select]
Re: GD malformed header error by RMGir (Prior) on Apr 04, 2002 at 14:07 UTC
The problem is that you're printing out the image directly to the output stream, without a "Content-type" prefix. The Content-type prefix is needed so the browser knows what it's dealing with, and webservers get annoyed if a CGI script doesn't output them correctly :) Adapted from the GD::Graph docs: `use CGI qw(:standard); #... print header("image/png"); binmode STDOUT; print $im->png;` [download] I think that will probably do it. -- Mike (Edit: Clarified what Content-type means)	[reply] [d/l]


We don't bite newbies here... much
	PerlMonks