[opencms-dev] Thumbnail images

Fri Oct 2 09:36:47 CEST 2009

The advantage of your current approach is that there is no issue with 
DoS attacks, since it all is controlled from within you template. You 
could probably make your template approach work with "Online" users as 
well if you keep a handle to a Offline-user somewhere, you would of 
course have to publish on the fly as well.

I agree that it is better to do it during the publish phase, as it 
allows you a better life time management, i.e. delete a thumbnail when 
the original image is removed and so forth.
Only thing is that in order to manipulate the list of resources being 
published, you need to hack your way around the fact that the 
CmsPublishList.add() is defined as  protected. I am not sure why, I have 
yet to see any ill effects of adding resources during the pre-publish 
event phase, but maybe I've just been lucky so be careful - you are 
going against the intention of the API.

Best regards
Claus

Paul-Inge Flakstad wrote:
> Hi Roman
> 
> Thanks for replying. :) It's reassuring to hear that OpenCms' native scaling does the trick for you. I suspect you've got a little more memory than we do, though - we had trouble with images smaller than 1 MB... (Many of our servers are running on VMWare, where memory is limited.)
> 
> Re-visiting this topic, I remembered a very interesting post from a while back: http://mail.opencms.org/pipermail/opencms-dev/2009q2/032196.html - it's about OpenCms' native image scaling enabling DOS attacks. 
> 
> Does anyone know if Alkacon ever did anything to remedy this? (I really liked the ideas of Sebastian & Claus, and Mika's implementation.)
> 
> Imagemagick I haven't heard of, but I might look into it if OpenCms' own API proves insufficient. Thanks for mentioning it.
> 
> About improving our routines for image generation: what I had in mind was actually exactly what you're suggesting - moving stuff out of the templates and into an event listener. That's the way it should've been from the start. I even tried it once, but eventually had to give up (it was my first action class for OpenCms, I ran into some problems). But it's only relevant if we decide to keep generating our image versions this way...and right now I'm leaning towards ditching the whole thing and just use OpenCms' native capabilities.
> 
> Again, thanks for sharing your experiences and ideas! :)
> 
> Cheers,
> Paul
> 
>> -----Original Message-----
>> From: opencms-dev-bounces at opencms.org 
>> [mailto:opencms-dev-bounces at opencms.org] On Behalf Of Roman 
>> Uhlig Maxity.de
>> Sent: 1. oktober 2009 17:01
>> To: The OpenCms mailing list
>> Subject: Re: [opencms-dev] Thumbnail images
>>
>>
>> Hi Paul,
>>
>> beside other minor use cases we are running a press service 
>> module, which uses native OpenCms image scaling for 
>> generating thumbnails of images up to 15 MB (pre-press). Up 
>> to now we never had any issues with it. Unless you need very 
>> special image scaling features, the native approach should be fine.
>>
>> On the other hand, you could use Imagemagick's Java API. We 
>> have some non-OpenCms Java web applications where we use it. 
>> It's quite easy and fun to use and offers a lot of features.
>>
>> Regarding the integration into the OpenCms workflow: I think 
>> there are several approaches. The one that comes to my mind 
>> first is hooking a suitable OpenCms event and do the 
>> generation there instead of praying that editors behave 
>> correctly (which will never happen I can tell). ;)
>>
>> Best regards,
>> Roman
>>
>>
>> -----Ursprüngliche Nachricht-----
>> Von: opencms-dev-bounces at opencms.org 
>> [mailto:opencms-dev-bounces at opencms.org] Im Auftrag von 
>> Paul-Inge Flakstad
>> Gesendet: Donnerstag, 1. Oktober 2009 16:40
>> An: The OpenCms mailing list
>> Betreff: [opencms-dev] Thumbnail images
>>
>> Hi list
>>
>> Just wanted to talk some basics! :) -I'm wondering how you 
>> handle your images, and in particular: your thumbnails.
>>
>> I am of course aware of the native image scaling feature 
>> provided by OpenCms, but somewhere along the line we decided 
>> upon "more control" (which we later discovered can be 
>> translated to "more messy"). We implemented a routine that 
>> keeps thumbnail files in the VFS, in sub-folders of 
>> "imagegallery" folders. 
>>
>> This is working OK..ish... -Editors sometimes forget to view 
>> the page they attached an image to before publishing. 
>> Whenever that happens, attemting to access the published page 
>> online will produce an error. (The thumbnail is created via 
>> the template, so no thumbnails of images for that page exists 
>> prior to the very first pageview.) Not to mention that there 
>> are a lot more files to handle.
>>
>> So, although the idea sounded good at the time, I'm not 
>> satisfied with our current solution.
>>
>> I have a couple of (obvious) choices:
>> 1.) Greatly improve routines for thumbnail generation / publishing
>> 2.) Fallback to using OpenCms' native image handling capabilities
>>
>> Do any of you guys handle thumbnail / images in ways I 
>> haven't thought of? 
>>
>> To those of you who are using OpenCms' parameter-based 
>> scaling for thumbnails: how is that working? -We had a lot of 
>> OOM exceptions when we used it, which is one reason we 
>> created the custom routines for thumbnail handling (we wanted 
>> more control over garbage collection).
>>
>> Hope some of you are willing to share! :)
>>
>> Cheers,
>> Paul
>>
>>
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