Dynamic images in Dreamwidth

[anarres]

This seems like it should be easy but I'm really stuck. I'm trying to dynamically display images - i.e. generate the image with a perl script and display it without saving it to the server.

This simple example works on my Heliohost server, but not on Dreamwidth (the example is from http://www.perlmonks.org/?node_id=18565):

--------test.shtml------------
<img src="test.cgi?size=100" alt="" />
------------------------------


--------test.cgi------------
#!/usr/bin/perl -w

use strict;
use CGI;
use GD;

my $cgi=new CGI;
my $cgi_size=$cgi-&gt;param('size') || '50';

print &quot;Content-type: image/gif\n\n&quot;;
my $gd=new GD::Image($cgi_size,$cgi_size);
my $blue=$gd-&gt;colorAllocate(0,0,255);
$gd-&gt;fill(0,0,$blue);
binmode STDOUT; #just in case we're on NT
print $gd-&gt;gif;
------------------------------


I'm stumped - has anyone got any ideas?

Comments

[exor674]

Dreamwidth environments don't actually execute perl / .cgi scripts under htdocs.

http://hg.dwscoalition.org/dw-free/file/cfe6c71e5611/cgi-bin/DW/Controller/CommentCount.pm is an example page that generates an image.

ETA: that sample uses Image::Magick, but you could use GD just as easy

[pauamma]

Yeah - as exor674 said, best way is to write a controller for a set of URLs representing the different charts. I'd put them in appropriate places for the pages they relate to, eg images for site stats accessible through http://www.dreamwidth.oerg/stats/foo, etc. Also need to decide who's responsible for extracting data. (controller for each image vs. controller for page itself, passing parameters to image congtroller through URL parameters.)

Going to look over the patches you uploaded, for things I need to point out that may still be applicable. Probably tomorrow.

[anarres]

Hmm... about deciding who's responsible for extracting data: if the controller for the page itself was responsible, would that mean the SiteStats controller would pass stats to views/stats/site.tt, which would then pass them to a graph-making controller module, which would then make the graph, which would then be displayed on site.tt? (My head hurts!)

[pauamma]

Something like that. stats.tt would output (at the appropriate location in the HTML source) something along the lines of <img src="http://www.dreamwidth.org/stats/piechart?free=2&amp;paid=3&amp;premium=5&amp;seed=7" alt=Pie chart: 2 free accounts, 3 paid, 5 premium paid, 7 seed" /> (URL scheme and item names meant as an example only).

:hands you some Tylenol.

[anarres]

Erm, but how do I get all that information (free=2 etc.) into the controller module that makes the pie chart?

If I navigate to piechart?free=2, does the information free=2 get passed to piechart.tt or to the controller module Piechart.pm?

[pauamma]

To the handler in the controller module. You can retrieve it with the following code in the handler:

my $r = DW::Request->get;
my $free = $r->get_args->{free};

For more information, see http://wiki.dwscoalition.org/notes/Routing_and_Template_Toolkit#Creating_a_handler_function

[anarres]

Thanks! I've got more of an idea about how to do this, but I still can't quite get it to work. The CommentCount controller contains this subroutine, which inserts the image into the webpage:


sub commentcount_handler {
my $r = DW::Request->get;
my $args = $r->get_args;

my $count = $args->{samplecount} || 0;

my $entry = undef;

if ( $args->{ditemid} && $args->{user} ) {
my $ditemid = $args->{ditemid};
my $uid = LJ::get_userid( $args->{user} );
$entry = LJ::Entry->new( $uid, ditemid => $ditemid ) if $uid;
}

$count = $entry->reply_count if $entry;

# create an image
my $image = Image::Magick->new;
$image->Set(pen => 'black');
$image->Set(font => 'Generic.ttf');
$image->Set(pointsize => 12);
$image->Set(size => '30x12');
$image->Read("label:$count");

# return the image
$r->content_type("image/png");
$r->print( $image->ImageToBlob( magick => "png" ) );

return $r->OK;
}


So I created a new controller module and attempted to write a version of this subroutine which would create an image with GD instead of with Image::Magick:

#!/usr/bin/perl

package DW::Controller::GDImage;

use strict;
use warnings;
use DW::Routing;
use GD;
use GD::Image;

DW::Routing->register_string("/test", \&my_subroutine, app => 1);
sub my_subroutine {

my $r = DW::Request->get;

# create an image
my $gd=new GD::Image;
my $blue=$gd->colorAllocate(0,0,255);
$gd->fill(0,0,$blue);

# return the image
$r->content_type("image/png");
$r->( print( $gd->png ) );

return $r->OK;
}
1;


This doesn't work. What's giving me problems is the line


$r->( print( $gd->png ) );


Which produces a page showing the error '[Error: Not a CODE reference at /dreamhack/home/8214-anarres/dw/cgi-bin/DW/Controller/GDImage.pm line 23. @ hack.dreamwidth.net]' - I take it this means that the thing in parentheses after the word 'print' should be a reference to a subroutine, but I'm not sure what I should do about this. At the top of the page are a bunch of symbols and letters starting with 'PNG' so I guess the images is being created, but somehow is being displayed as raw data rather than as an image.

For comparison, the version of this that works in a non-Dreamwidth environment (the one in my original post is a bit wrong) is:


#!/usr/bin/perl -w
use GD::Image;

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

my $gd=new GD::Image;
my $blue=$gd->colorAllocate(0,0,255);
$gd->fill(0,0,$blue);
print $gd->png;


[fu]

Hmm, try $r->print( $gd->png );

It's erroring because it thinks you're trying to call $r as a function, with this line: $r->();

[anarres]

It worked, thanks!!

[fu]

Great! You're welcome *g*