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Subject: Re: [office] Proposal for modification of preview image description
Hi, first of all, thank you very much for all the feedback to the proposal. I'm answering to this particular mail, because I think the suggestion from Florian/Hubert Figuiere provided a very good basis for refining my proposal. However, this mail should be seen as a reply to the other mails regarding this topic as well. Actually, I think I should have provided some more rationales for the proposal: The reason for proposing to change the specification at all was that it turned out that some operating systems allow to display thumbnails in boxes that are larger than 128x128 pixels. As Florian/Hubert Figuiere correctly mention, the thumbnail specification at freedesktop.org allows 128x128 and 256x256 pixels. Microsoft Windows Vista also allows thumbnail boxes up to 256x256 (at least that is what I have been told). And 128x128 pixel thumbnail upscaled to 256x256 simply look bad. Therefore, the rational behind the proposal actually was to support larger thumbnail images than 128x128 pixels. The idea never was to support smaller ones. I thirst thought about adding 256x256 pixels as an option, but decided against that. The reason is that the two examples provided above are just two examples. Other operating systems may use other thumbnail sizes, and who knows what sizes will be used in future OS versions, let's say in a year or two? In addition, the thumbnail image size has an impact on the document size. The larger the image gets, the larger the documents get. That may not be an issue for desktop systems, but may be for small devices storing many small documents. So, taking it all together, the "optimal" thumbnail image size depends on many factors, and it seems to be reasonable to me to allow implementors/users to choose an image size that is appropriate for their use case and platform, rather than to require a certain one in the specification. The same applies to other PNG parameters that we have in the specification. However, I also agree that with the text I have proposed, any guidance what an appropriate image size may be is lost, and that this may be an issue. To resolve this issue, I like Hubert Figuiere's idea to say in which resolution thumbnail images are typically displayed, rather than recommending any image sizes. I therefore suggest to add a the following (non-normative) note to the (normative) text I have proposed: "Note: Current desktops display thumbnail images within squares of up to 256 pixel width and height. While this specification does not define upper or lower limits for thumbnail image sizes, implementations should only use image sizes that are displayed with a reasonable quality if scaled to fit into 256x256 pixel square." Well, this probably can be said in better words. I'm very open for suggestions. A normative minimum size seems not to be required in that case, because the note makes already clear that a 33x32 pixel image will not be the best choice. Some more comments are inline. Florian Reuter wrote: > Dear TC, > > here a some comments from my colleague Hubert Figuiere who knows more about this then me: > > <snip> > The thumbnail size shouldn't be limited by the spec, because it does not > make sense to do so. > On the other hand, the file format MUST be PNG. (MUST is stronger that > SHALL, isn't it?) MUST equals SHALL, but the ISO directives ODF is using does only know SHALL. The less strong term is SHOULD. > Ideally the spec could state that the recommended size is, for now, to > be enclosed in a 256x256 rectangle (document pages are not square) in > order to allow down-scaling the original thumbnail, but the size is to > be implementation specific and thumbnailer should NOT depend on it. This > would allow increasing the default size without changing the spec. I > don't see why we would need alpha transparency. > > Below is a link to the thumbnail spec which give a good idea of what is > going on on the freedesktop.org side: > http://jens.triq.net/thumbnail-spec/index.html > IMHO this spec should be used as a guide. Well, it has been used as a guide, and the ODF 1.0 specification actually referenced freedesktop.org. However, because this is not really a standard, the reference has been removed for formal reasons. > > > Hub > </snip> > > Best regards, > > ~Florian Best regards Michael -- Michael Brauer, Technical Architect Software Engineering StarOffice/OpenOffice.org Sun Microsystems GmbH Nagelsweg 55 D-20097 Hamburg, Germany michael.brauer@sun.com http://sun.com/staroffice +49 40 23646 500 http://blogs.sun.com/GullFOSS Sitz der Gesellschaft: Sun Microsystems GmbH, Sonnenallee 1, D-85551 Kirchheim-Heimstetten Amtsgericht Muenchen: HRB 161028 Geschaeftsfuehrer: Wolfgang Engels, Dr. Roland Boemer Vorsitzender des Aufsichtsrates: Martin Haering
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