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Photo: somes issues and thoughts
by J M Cerqueira Esteves 13 Jan '02

13 Jan '02

Greetings I am developing a site where people editing content will not directly access the Zope interface but will use several simplified forms adequate for their work. Since they will occasionally need to add some images, I am using the Photo product as the basis for the image management tool they will be using (images will be Photo objects in a hierarchy of Photo Folders, and most people will not be writing DTML but referring to original images or derived displays explicitly writing their URLs in plain HTML). While preparing this, I noticed a few minor issues. On-the-fly resizing could be interesting: Ron Bickers seems to be considering adding support for on-the-fly image resizing, that is, arbitrary image resizing with no need for predefining named display sizes. This could be convenient for situations like my current one. There will be a few cases where the "photo album" metaphor will be used (like in the Photo Folder sample views), but the majority of the other pictures will be added one by one to be used in separate contexts, each in one or two sizes without any foreseeable "size standards". For many pictures, display sizes will have to be defined individually, therefore with less interest in having to "invent" or reuse a name for each new size or even to have to visit an administration interface just for resizing; maybe the nicest solution from the point of view of a content editor (when not working with the "tag" method but only writing pure HTML) would be simply to write <img src="http:/somesite/img/.../picture.jpg?width=300" ... /> when one needs to show picture.jpg in a new size with width of 300 pixels or .../picture.jpg?width=480&height=480 to limite the larger size to 480 pixels. This would end up producing "unnamed" cached displays for each picture. Of course HTML authors would still have to take care of checking the final dimensions in order to write 'height' and 'width' attributes... or those could be supplied by a size testing interface on the site (possibly listing already cached sizes). It could also be nice to allow rescaling (relatively to the original size) with something like .../picture.jpg?scale=1.56 (or a "scale" cookie perhaps of use for automagically resizing all images (big and small) by the same factor on a set of pages via a "scale" cookie). One could then wish for several other image transformations like those available with \includegraphics in LaTeX package graphicx: cropping with "bounding boxes", rotation, ... :-) About the cookie name: It could also be useful to allow customization of the cookie name (now hardcoded as 'display') to solve possible cases of "collision" with other cookies or even to allow separate display customization for different image sets in the same site. Likewise for any other cookies which may someday be used by the Photo product. The `tag' method: The `tag' method sets the display cookie only when the supplied display name corresponds to an existing one for the current image. An interesting exception would be to set the display cookie ALSO when display=='', thus activating "natural size" viewing (unless one has defined a display size with id=='', which is currently possible...). Ideally, the `tag' method should respect alt=='' (since sometimes one really wants that): if alt is None: alt = getattr(self, 'title', None) if alt is None: alt = self.getId() Image size calculation: In my "view" method (replacing the sample "view") I was going to show the dimensions the current pic would have at each defined display size, near to the link to the corresponding page. It would be interesting to have public methods providing that information (height() and width() only provide it for the original image; displayMap() only provides dimensions for displays which have already been generated, and I chose not to pregenerate them all). I simply reproduced the calculations of _getAspectRatioSize, but then noticed that some results were wrong. For instance, with an original image of 272×281 pixels, the result of rezising to a maximum of 480×480 is not an image with 464×480 as expected, but 464×479. This happens because I opted for using ImageMagick and: - _getAspectRatioSize, using integer division, rounds down 464.626334... (the "ideal" new width) to 464; - _resize calls ImageMagick's `convert' with option -geometry 464x480; - called like this, `convert' also tries to mantain the aspect ratio of the input image and uses the -geometry parameters as limits: constrained to 464×480, the best solution it finds to maintain the aspect ratio is creating an image of 464×479. It would be better in this case to call `convert' with option -geometry 480x480 and let it calculate the ideal new size. When I do that manually, I get a 465×480 image. Unfortunately, I had no time to determine the precise equation used by ImageMagick to calculate new sizes maintaining aspect ratio. Having it, you could use that instead of the calculation at _getAspectRatioSize when resizing with PIL (since PIL's `resize', unlike ImageMagick's `convert', doesn't try to maintain aspect ratio and needs to be given precise final sizes). Image quality with PIL: I noticed that in the version of PIL I have here, 1.1.2, the resize method has an optional filter argument which can be "NEAREST, BILINEAR, or BICUBIC. If omitted, it defaults to NEAREST." I have no time for careful testing now (and Image Magick is working very well), but noticed that `resize' is being without specifying the filter, thus using NEAREST and not taking full advantage of PIL capabilities. Best regards J Esteves

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Passing arguments when calling precondition
by Jánvári Gusztáv 12 Jan '02

12 Jan '02

Could anybody tell me a reliable method on how to pass arguments for a script/method employed as precondition for some File objects? What I'd like to do is to pass a record identifier to the method called as precondition, increase a download counter in a database, then let the visitor download the given file. If the record identifier would be None, an exception could be thrown, thus denying access to the file. In this case I wouldn't bother with users who try to enter absolute URL with a valid record identifier known e.g. by accident for the files requiring registration before downloading, since the download counter would work and that's all what I want. e-Musty

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RE: [Zope] Corrupt ZODB on W2k
by Tom Cameron 12 Jan '02

12 Jan '02

Chris, => Have you tried checking your backups to pinpoint when the corruption => happened? To be honest, the problem is in a client's machine and has only happened twice in a year. They are not willing to pay me to investigate and I just dont have the time for such work. => One final thing, I find it interesting that exporting and => importing seems to fix your problem. More interesting, I find that export+import as .zexp does not work, but exporting+import as .xml does work. I really dont know much about the difference, but the .zexp seems to just grab a chunk of the ZODB errors and all, but .xml is a true export of the data. Anyway, I sent this message off for discussion purposes, we have fixed the problem and moved on. I am just curious about why this happened and if others have similar experiences. Tom

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Exporting or saving File object to the server's local file system from Zope
by e-Musty 12 Jan '02

12 Jan '02

I have several files stored in a Folder, but I gonna to use a LocalFileSystem object to hold those files. Since the server is a bit far away from my chair, I wouldn't like to play with downloading files one-by-one from Zope, then upload those to the server. Could somebody tell me a way, how to export files of a folder to the server's file system? Standard Import/Export functions has two problems, namely that (a) even if exporting a single File, it will be saved as a zexp, and that (b) LocalFileSystem does not support paste or import/export (only cut and copy). All hints appreciated, e-Musty

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ZOQL Feedback
by Stephan Richter 12 Jan '02

12 Jan '02

Hello everyone, after I released ZOQLMethod 0.4.0 dev preview, some people voted in the online poll that they did not like ZOQL, since it is inconsistent. Unfortunately, I did not provide a comments field, where people could elaborate some more. Therefore I am writing to the list asking people of why they think about ZOQL the way they do negative and positive and I hope that Thomas Foerster (really the main developer behind ZOQLMethod, having written the Parser and much more) and I will be able to implement the suggestions. We both want that product to be useful. It should help the user (you) to develop your applications quicker and fill in a major hole in the framework (i.e.: provide a query language for the ZODB). Thanks a lot for your time! Regards, Stephan -- Stephan Richter CBU - Physics and Chemistry Student Web2k - Web Design/Development & Technical Project Management

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Auto render validated values in Formulator
by Trevor Toenjes 12 Jan '02

12 Jan '02

I am trying to auto-render the results of a form. <dtml-call "form.validate_all_to_request(REQUEST)"> <dtml-in "form.get_fields()"> <dtml-let field=sequence-item> <dtml-var "field.get_value('description')"><br> <dtml-var field><p> <----offending dtml </dtml-let> </dtml-in> However, this displays nothing for 'field'. <dtml-var "field.render_from_request(REQUEST)"> displays the values, but in the full HTML form (undesired) Manually, <dtml-var myfieldname> renders properly, so I am being tripped up by object types. What am I missing? TIA -Trevor

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Tree tag and lists.
by Josef Meile 12 Jan '02

12 Jan '02

I want to create a bullet list with the tree tag. My idea is to have a list of topics which can be expanded and collapsed. Each time the user clicks on a collapsed node, a text will be shown. My problem is that I don't know how I can use this tag with a list, ie: [['Title1','description1'],['Title2','description2'],...,['Titlen','descriptionn']] Does somebody have an idea? Thanks in advanced, Josef.

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Script (python) shows transaction for adding folder
by Tim Hicks 12 Jan '02

12 Jan '02

I have a script that accepts an html form entry (submitted from a dtml-document) and tries to do various file uploads into the zodb (actually, they are ExtImages). All of this works (pretty well), but in testing, I've noticed that each time my script performs this form validation/submission process, there is a new transaction present in the undo list. The transaction refers to adding a folder (and probably another one to add the actual image) to the zodb for the upload. So, my question is, why does the transaction appear in the undo list for the script, and not the parent folder I'm adding to (which is a BTree folder if that makes any difference)? I guess it's not a problem, just seems a bit odd to me. thanks tim

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[ANNOUNCEMENT] Indian Zope and Python User Group
by Kiran Jonnalagadda 12 Jan '02

12 Jan '02

Hi all, There is a new Zope and Python User Group for Indian users. The community currently has only a mailing list hosted at Yahoo Groups but a Web site is also in the pipeline. It would be nice to have some of you folks over on the list to help participation take off. The list's address is: http://groups.yahoo.com/group/izpug To subscribe, send a blank message to: izpug-subscribe(a)yahoogroups.com Thanks! -- Kiran Jonnalagadda http://www.pobox.com/~jace

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Corrupt ZODB on W2k
by Tom Cameron 12 Jan '02

12 Jan '02

A client of mine insisted in running Zope on Win2k, so I installed Zope 2.3.4 (some time ago) on their server and also a few products/sites I built for them. The machine has been running now for about 8 months. They don't change much, but it is relatively heavily loaded. They pack the ZODB monthly and backup regularly. On two occasions in the past 8 months, we have noticed very peculiar permissions problems. Several months ago, all of a sudden, several of the users could no longer access the ZMI. Also sections of the site returned permissions errors for no reason. Sometimes specific DTML methods simply refused to display with permissions errors. After many hours of investigating we found no possible logic to this. I then exported the entire ZODB and re-imported it all into a fresh ZODB. All was fine again. Now, several months later the same problem has re-appeared. Again they get weird permissions errors on certain objects, but no real logic or pattern to the errors. Creating new users does not always work. Old users get locked out. Some DTML methods will not work. It looks very much like the ZODB simply gets corrupt over time. I can fix this by exporting-importing again, but I am wondering if anybody else has any experience of a similar problem or solution? Tom

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