Re: [djatoka-devel] djatoka calling images: scale versus size

[<rc...@gm...>]

Hi Phil,

Scaling (1st and 2nd way, via svc.scale) unfortunately does have a performance and quality penalty.  The third way just grabs the chunk out the the jp2 file and converts it to the requested file format (e.g. jpg).  The first two methods using svc.scale require djatoka to grab the chunk out the the jp2, downsize the image by 0.1 - 0.9999 to accommodate the scaling request.  I understand why people want it, but I'd only use it for when you want to render something fullscreen.  

Sorry I can't be of more help and let me know if you have any other questions.

Cheers,
Ryan

On Oct 5, 2010, at 1:05 PM, phil cryer wrote:

> Ryan
> One of developers was working with djatoka on a new viewer for one of
> our sites and he had this behavior when calling the images via scale
> (size, percentage) versus just size. (see text below) Does this make
> sense? Why does the 3rd way 1) run the fastest 2) look the best - and
> is this expected? Also, are we using djatoka right in this instance?
> 
> Thanks
> 
> P
> 
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> For the image conversation later today, here are links demonstrating the
> problem I was describing to you yesterday.
> 
> Basically, when you try to retrieve an image using svc.scale (the first
> 2 links below), it looks really noisy.  If you use svc.level (which is
> what the image viewer uses - the last link), it looks quite good.
> 
> Using svc.level means that you must request an image size that is a
> factor of 2 reduction of the original image.  So, you cannot request a
> fixed size thumbnail.
> 
> Thanks,
> Jay
> 
> Request using scaling by fixed number of pixels:
> http://mbgserv18.mobot.org/adore-djatoka/resolver?url_ver=Z39.88-2004&rf
> t_id=http://mbgserv09:8057/TropicosImages2/255/25509881_006.jp2&svc_id=i
> nfo:lanl-repo/svc/getRegion&svc_val_fmt=info:ofi/fmt:kev:mtx:jpeg2000&sv
> c.format=image/jpeg&svc.scale=1024
> 
> Request using scaling by proportion (factor of 2):
> http://mbgserv18.mobot.org/adore-djatoka/resolver?url_ver=Z39.88-2004&rf
> t_id=http://mbgserv09:8057/TropicosImages2/255/25509881_006.jp2&svc_id=i
> nfo:lanl-repo/svc/getRegion&svc_val_fmt=info:ofi/fmt:kev:mtx:jpeg2000&sv
> c.format=image/jpeg&svc.scale=.25
> 
> Request using levels
> http://mbgserv18.mobot.org/adore-djatoka/resolver?url_ver=Z39.88-2004&rf
> t_id=http://mbgserv09:8057/TropicosImages2/255/25509881_006.jp2&svc_id=i
> nfo:lanl-repo/svc/getRegion&svc_val_fmt=info:ofi/fmt:kev:mtx:jpeg2000&sv
> c.format=image/jpeg&svc.level=3&svc.rotate=0&svc.region=0,0,1024,1024
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> 
> P
> -- 
> http://philcryer.com
> 
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