[annotator-dev] Request for discussion: non-text annotations?

Robert Casties casties at mpiwg-berlin.mpg.de
Mon Nov 26 16:57:37 UTC 2012

On 25.11.12 03:57, Randall Leeds wrote:
> On Thu, Nov 22, 2012 at 3:59 AM, Robert Casties <casties at mpiwg-berlin.mpg.de
>> wrote:
>> Hi Rainer,
>> On 22.11.12 12:08, Simon Rainer wrote:
>>> +1 on the 'units' extension. 'fraction' and 'pixel' for the time
>>> being? (I'm also thinking about our use case with OpenLayers, which
>>> works with map coordinates. So this might be a nice way to handle
>>> those cleanly.)
>> Sounds good to me. So Openlayers uses lat/lon coordinates?
> In terms of practical examples, Open Annotation has a wiki that's sort of
> buried over at the W3C site. In this example, both Well-Known-Text and SVG
> are used to select part of a map. It might give us some inspiration:
> http://maphub.github.com/api/#comment_example

Interesting examples. They seem to be afraid to show their full SVG :-)

I like the application/wkt polygon stuff (no mention of units though). I
had been thinking of fragments like "#poly:x1,y1,x2,y2,..." but this
seems nicer.

>>> Regarding shape alternatives: hm. I still need to think through the
>>> entire case first I guess. But rather than having alternatives, I
>>> think, I'd simply add extra properties to the shape itself. Say
>>> something like:
>>> shape : { type : 'Polygon', geometry : { units : 'pixel',  coords:
>>> [{x: 10, y: 10}, {x: 100, y: 10}, {x: 100, y: 20}, {x: 10, y: 20}]
>>> }, anchorPoint: 0 }
>> Looks Ok to me. A small thing: I would like to use a lower case type
>> "polygon" similar to the SVG spec.
>> I like your explicit coordinate pairs for polygon.
> +1.
> I'll defer judgment on whether it's best to use a string or a series of x-y
> objects, but I wonder if including units is useful? Couldn't we just
> specify that they are always normalized to 0-1 range? Is there a good
> reason not to do this? One advantage I see is that it makes it possible to
> apply the shape to a scaled image without knowing the scale / the size of
> the original. This seems the simplest thing to me.

I a purely rational world I would agree :-) (that's why digilib has been
using normalized coordinates for 10 years)

Buts lots of other tools, including http://www.w3.org/TR/media-frags/
simply use pixels (or integer percent!!!), so I would like to make the
choice as obvious as possible.

Also I think it doesn't hurt, we could define units=fraction to be the
default if omitted and be open to units=WGS84 or some such.


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