[MEI-L] Coordinate system confusion

Martha Thomae thomaemartha at gmail.com
Tue Jul 4 18:40:56 CEST 2017

Sorry to intrude, but when reading this a question popped into my head.
Is it possible to use @vo or another attribute to change the line in which
a <rest> lies? This will help me with something I am working on.

Thank you!


On Tue, Jul 4, 2017 at 11:16 AM, Daniel Alles <
DanielAlles at stud.uni-frankfurt.de> wrote:

> Thank you, Johannes, that really helped and made that clear. So I can
> continue using the Edirom-coordinates for ulx etc.
> Zitat von Johannes Kepper <kepper at edirom.de>:
> Dear Daniel,
>> that's a real confusion, and we need to make it clearer in the
>> guidelines. *Pixel* coordinates are always with the origin in the top left
>> corner. *Music* coordinates, however, are always bottom up. @ulx and so on
>> are always in pixel units, but @vo (vertical offset) is specified in
>> interline distances (half the distance between two staff lines, or, in
>> other words, the vertical distance between a C4 and a D4, or any other two
>> adjacent notes). If you want to specify that a dynamic is written above its
>> default position, it seems more natural that values go up (i.e., @vo="3").
>> This means that for musical units the origin has to be bottom left. I know
>> it's confusing in the guidelines, and we will address this at some point.
>> If you don't mind, you're invited to prepare something on Git and submit a
>> pull request ;-)
>> Hope this helps,
>> jo
>> Am 04.07.2017 um 14:48 schrieb Daniel Alles <
>>> DanielAlles at stud.uni-frankfurt.de>:
>>> Dear all,
>>> at the moment, I am a little bit confused about how MEI defines its
>>> coordinate system: It is possible to add the attributes @ulx, @uly, @lrx
>>> and @lry to for example a surface, as written in part 12 of the Guidelines,
>>> which places the origin of the coordinate system in the upper left corner.
>>> All the examples in that part show that behavior, ulx/uly is always 0/0.
>>> This would correspond to the coordinate systems used in SVG and DOM and
>>> (which is what I use for my work) Edirom Editor. On the other hand it is
>>> written in part 22.3, that MEI uses a coordinate system in which "the
>>> y-axis points from bottom up". That would mean, that ulx/uly could never be
>>> 0/0.
>>> So now my questions: Is it sufficient to use the coordinates like in the
>>> examples, with the origin in the upper left corner? Would that "override"
>>> MEIs original coordinate system? If not: Isn't the possibility to encode
>>> areas from top-left to bottom-right corners a semantic error in MEI, if the
>>> coordinate system is pointing from bottom-left to top-right?
>>> Best,
>>> Daniel
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*Martha E. Thomae*
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