Easy Pixel PNG Generator

[bladx]

Category:

CGI Programming

Description:

This is based on a totally random programming idea from Vynce. All this does, is it is a CGI, that lets a user enter in some values for the name of the new generated png that will be created after filling the info. and the hex values for the color of the pixels. It then does the creating of the px png for you, and can be used for generating one color 1x1px png backgrounds as well, for those of you that may need something handy like this, (since I tend to do stuff like this as well.)

Overall, this is a very simple utility, but a fun one to use (or at least resourceful,) if you need to make some quick one color backgrounds ever.

#!/usr/bin/perl -w
use strict;
use warnings;
use CGI;
use GD;

my $query = new CGI;

print $query->header;
print $query->start_html("EasyPX Generator");
print "<H1>EasyPX Generator</H1>\n";
prompt($query);
go_for_it($query);
print $query->end_html;
 
sub prompt {
  my($query) = @_;

  print $query->startform;

  print "Enter Image File Name&nbsp;&nbsp;";
  print $query->textfield('name'),"<br>";

  print "Enter Width&nbsp;&nbsp;";
  print $query->textfield('width'),"<br>";
 
  print "Enter Height&nbsp;&nbsp;";
  print $query->textfield('height'),"<br>";
  
  print "Enter Red Hex Value&nbsp;&nbsp;";
  print $query->textfield('red_value'),"<br>";
  
  print "Enter Green Hex Value&nbsp;&nbsp;";
  print $query->textfield('green_value'),"<br>";

  print "Enter Blue Hex Value&nbsp;&nbsp;";
  print $query->textfield('blue_value'),"<br>";

  print "<p>",$query->reset;
  print $query->submit('Action','Submit');
  print $query->endform;
  print "<hr>\n";
}

sub go_for_it {
  my($query) = @_;
  my(@values,$key);

  print "<H2>Completed with the following values.</H2>";

  foreach $key ($query->param) {
    print "<STRONG>$key</STRONG> -> ";
    @values = $query->param($key);
    print join(", ",@values),"<BR>\n";

    if ($key =~ /name/i) {
      our $name = $query->param($key);
    } elsif ($key =~ /width/i) {
      our $width = $query->param($key);
    } elsif ($key =~ /height/i) {
      our $height = $query->param($key);
    } elsif ($key =~ /red/i) {
      our $red = $query->param($key);
      $red = oct "0x" . $red;
    } elsif ($key =~ /green/i) {
      our $green = $query->param($key);
      $green = oct "0x" . $green;
    } elsif ($key =~ /blue/i) {
      our $blue = $query->param($key);
      $blue = oct "0x" . $blue;
    }
  }

  my $im = new GD::Image(our $width,our $height);

  my $color = $im->colorAllocate(our $red,our $green,our $blue);
  $im->fill(1,1,$color);
  
  open IMAGE, ">" . our $name . ".png";
  print IMAGE $im->png();
  close IMAGE;
}

[ajt]

Err, this doesn't actually work! For those of us forced to labour under a Microsoft cloud, you can't just print binary files out without turning binmode on. Thus you need to change the print statement at the end to:

  open IMAGE, ">" . $name . ".png";
  binmode IMAGE;
  print IMAGE $im->png();
  close IMAGE;

You have also loaded CGI but then gone on to print out your own HTML. It seems a bit much having a dog, and barking yourself, if you ask me.

Also sin of sins, you are writing to the file system, with a user supplied filename and not doing any taint checking. I know you said this was a "simple utility", but you should not allow anyone to write to your filesystem, without being sure that they are writing what and where you want to allow them. See perlsec.

I think merlyn wrote a pixel factory on his column, which is similar in idea.

Your script is however, minor defects aside, quite useful.

[bladx]

Ok, 3 things:

I originally had binmode in there ... but took it out after forgetting to keeping it in.

I used CGI.pm for the parsing ... hmm.

Yes, I did not use taint checking, I admit it.

This was just a quick utility based on someone's idea, I have no intention of adding or subracting to it as of this moment, but thanks for the delayed response, ajt.

Andy Summers