Dear David,
In the Online Froissart we use small JPEGs at screen resolution (calculated assuming the highest resolutions on common commercially available systems, see for example http://en.wikipedia.org/wiki/Display_resolution).
For more sophisticated image viewing, which allows zooming, we use the Virtual Vellum manuscript viewer, which was developed for our project (see http://www.hrionline.ac.uk/onlinefroissart/apparatus.jsp?type=vv). Is is written in Java, so requires Java to be installed on the machine used to access the images, but most computers these days have this. The obvious advantage is that it will run on any system that can run Java. Our default full image resolution size is 600 dpi (relative to the original MS, which means 150 MB in TIFF and about 6MB in slightly lossy JPEG2000, although some image collections provided by partners are at 300 DPI).
For our project we deploy the viewer in a separate window, but it can also be embedded in browser pages (see http://cbers.shef.ac.uk/manuscripts/index.html). Apart from possibilies of zooming and displaying many images side by side (in stand-alone windows only), Virtual Vellum can measure areas of the page (size of initials, colums etc.). It is also possible to display transcription (and even translation) as a separate layer within the Virtual Vellum viewer (check this out on Besancon MS 865). Transcription (and translation) will respond to changes in the images and therefore zoom in and change view when you change the main image view.
The native image format used by Virtual Vellum is JPEG2000, but the software comes with a utility to create JPEG2000 libraries of images from several input formats (including TIFF and JPEG).
Virtual Vellum is freely available for non-commercial use by single users or projects. It can be used on local images collections or embedded as a Java-applet for web display (for links to documentation and downloads, see http://www.shef.ac.uk/hri/projects/projectpages/virtualvellum).
Godfried Croenen
-- Dr. Godfried Croenen Department of Cultures, Languages and Area Studies University of Liverpool Chatham Street Liverpool L69 7ZR United Kingdom Tel: +44 (0)151 794 2763 Fax: +44 (0)151 794 2357 e-mail: G.Croenen@Liverpool.ac.uk Personal webpage: http://www.liv.ac.uk/~gcroenen/index.htm Online Froissart: http://www.hrionline.ac.uk/onlinefroissart/
-----Original Message----- From: dm-l-bounces@uleth.ca [mailto:dm-l-bounces@uleth.ca] On Behalf Of Birnbaum, David J Sent: 19 June 2012 01:42 To: dm-l@uleth.ca Subject: [dm-l] best practice: photographc facsimile?
Dear Digital Medievalist,
For a couple of new Internet editions of medieval manuscripts I've procured high-resolution tiff images, which I'm publishing with a "magnifying glass" overlay. This is in a "responsive" context, so the components of the page, including the images, resize to fit the window dimensions. There's a sample at:
http://suprasliensis.obdurodon.org/pages/supr001r.html
The current images were prepared quickly for a demo, and are not of consistent size or resolution. I would now like to go back to get this part of the site up to production quality, and I would be grateful for advice about how to manage the images, an area where I don't have much (= any) knowledge of best practice. I'd like small image files that load quickly, and I think I don't mind slightly lossy compression if that would reduce the file size substantially--but if that's a mistake, I'd be grateful for a warning. I think there are two questions:
1. What's an appropriate file format and resolution (size, dpi, color depth, etc.) for the base image, the one that is displayed in full to the right of the transcription, and that resizes as the user resizes the window? Currently the image files are in jpg format and vary in size from about 2M down to 250k. I can regenerate them all at a common size, resolution, color depth, etc. from the original tiffs, but I don't know whether there is any sense of best practice concerning what that size should be. If I go the lossy route, what's a reasonable value?
2. What's an appropriate degree of magnification for the magnifying-glass inset view? Currently the magnifying glass inset always shows the image at 200% of the actual file size (not the size of the page as displayed without magnification in the browser window!). You can see the difference by comparing, say, folio 30v (about 2MB) to 284r (about 270k), where the magnification is much greater in the former than the latter. I can set the level of magnification anywhere I'd like, but is there any agreement about best practice here?
By way of orientation in the question: the purpose of the full image is to allow the user to see the image conveniently alongside the transcription, verifying any moments where our editorial judgment might appear surprising or questionable. The point of the magnified inset is to let the user examine details that may not be visible at lesser magnification, such as erasures, corrections, etc. My casual impression is that 30v looks pretty good and loads reasonably quickly (although quicker would be better), but I don't place great confidence in my own casual impressions.
Thanks,
David djbpitt@pitt.edu
Digital Medievalist -- http://www.digitalmedievalist.org/ Journal: http://www.digitalmedievalist.org/journal/ Journal Editors: editors _AT_ digitalmedievalist.org News: http://www.digitalmedievalist.org/news/ Wiki: http://www.digitalmedievalist.org/wiki/ Twitter: http://twitter.com/digitalmedieval Facebook: http://www.facebook.com/group.php?gidI320313760 Discussion list: dm-l@uleth.ca Change list options: http://listserv.uleth.ca/mailman/listinfo/dm-l