http://www.perlmonks.org?node_id=827069

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

I am using Imager to dynamically create thumbnails of jpegs. However when some images are resized it adds blocks of transparent colors over it, or even cuts off complete pieces of the images. Some images it won't even resize, which it is telling me 'Couldn't render image: Bogus DQT index 11'. But I can still view the images in photoshop, web browsers, etc.

Is this a problem with Imager or with the jpeg library it uses?

I would just use image magick to permanently create the thumbnails as they are uploaded, except every time I try to install it via cpan it errors asking for me to insert a disk (wtf?), and ppm doesn't have Catalyst::Plugin::Upload::Image::Magick::Thumbnail. ImageMagick has just been a giant pain in the ass on win32 and i'd like to avoid it.

Anyone have any ideas on the Imager problem, or any other solution I could implement? I am developing on win32 using strawberry perl 5.10.

Replies are listed 'Best First'.
Re: Creating thumbnail solution help
by almut (Canon) on Mar 05, 2010 at 21:34 UTC

    Are you sure you're handling your image data always in binary mode?  For example, reading them in in text mode might well produce broken images.  Just a guess, though...

[reply]
Re: Creating thumbnail solution help
by tonyc (Friar) on Mar 05, 2010 at 22:36 UTC
    Posting the code you're using and a link to one of the problematic images would be useful.
[reply]
      Here is an image: http://img707.imageshack.us/img707/2011/picture066q.jpg The code im using is 
      sub thumbnail :Regex('^thumbnail/(.+)') {
    my ($self, $c) = @_;
    my $image_id = $c->req->captures->[0];
    
    $image_id =~ s/\//\\/g;
    
    my $image_obj = $c->model('File')->slurp($image_id)
        or $c->detach('/default');

    $c->stash->{scaling} = 'fit';
    $c->stash->{x}     = 100;
    $c->stash->{image} = $image_obj;
    
    $c->forward('View::Thumbnail');
 }

      [download]
      It can also be seen on the author's site here: http://perl.jonallen.info/writing/articles/creating-thumbnails-with-catalyst It opens the file using Catalyst::Model::File. I don't see any parameters to set it to binary, so maybe that is why. But the tutorial on the author's page above doesn't mention anything about having to set the file model to binary so I dunno...
[reply]
[d/l]
        It is indeed a problem with Imager or the jpeg library it uses. I don't know if its only on a windows platform or not though. Instead i've wrote a catalyst view that uses Image::Resizer instead of Catalyst::View::Thumbnail which uses Imager.
[reply]

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