[MEI-L] coordinates

[Andrew Hankinson, Mr]

Hi Thomas,

We're currently using MEI to in an optical music recognition application, and relating the graphical musical symbols (from a scanned book) to the semantic "interpretation" of these symbols via the <facsimile> system that Johannes mentions.

Basically, within facsimile you define a number of bounding boxes using <zone>, defined by ulx,uly/lrx,lry coordinates. These all have a unique ID. Then on every musical element, you use the @facs attribute to refer to the unique ID of the corresponding zone.

We recently did a bit of looking, and apparently in similar applications to ours (METS/ALTO), the standard metric unit is tenths of a millimeter. This gives you the ability to work with integers at a very fine level while maintaining resolution independence. This is not similar to MusicXML's "tenth," which is 1/10th the height of inter-line staff space (i.e., a tenth is equal to 1/40th of a five-line staff).

I don't know if this is at all what you are describing, but I hope it helps!
-Andrew


On 2011-02-23, at 7:20 AM, Johannes Kepper wrote:

> Hi Thomas,
> 
> MEI has different approaches to graphics. When you plan to describe an existing image, you should use the @facs-attribute and refer to a zone-element in facsimile (sibling of body). I don't think that this is what you're looking for, but it is surely the better established way to deal with graphics in MEI. The other way is what you already mentioned: Using @x / @y. The unit of this is not clearly defined, but it makes a lot of sense to refer to the unit defined in scoredef. In scoredef/@page.units you can decide whether to use cm / mm or inches. Adding pix to that list would require to specify the resolution (which is not possible yet, I think). There are lots of other interesting attributes for you on scoredef when you consider to render your MEI. The origin for your @x / @y coordinates would be the upper left corner of the page (even though the current documentation does not say so, unfortunately…). 
> 
> I hope this helps you a bit to get things started. Please ask if you have any further questions – I'm happy to hear more about your project!
> 
> Best regards,
> Johannes
> 
> 
> Am 23.02.2011 um 11:18 schrieb TW:
> 
>> Dear MEI list members,
>> 
>> I'm exploring different approaches to music encoding and am especially
>> interested in the relationship between graphics and semantics as well
>> as graphical flexibility and precision.
>> 
>> One basic question about the graphical capabilities of MEI is how the
>> x/y coordinates are meant to work.  What is the "output coordinate
>> system" that the schema talks about?  Is it page based, staff based
>> like in SCORE, staff/measure based like in MusicXML or maybe dependent
>> on context?  Is there a standard unit like MusicXML's "tenth" or is
>> the encoder free to choose units of his liking?
>> 
>> Thanks
>> Thomas Weber
>> 
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> 
> 
> 
> ------------------------
> Dr. Johannes Kepper
> Wiss. Mitarbeiter
> DFG-Projekt Edirom
> 
> Musikwiss. Seminar Detmold/Paderborn
> Gartenstr. 20
> 32756 Detmold
> 
> Tel. +49 5231 975665
> Mail: kepper at edirom.de
> 
> 
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