Hi,
I'd like to extend the uom extension to SLD so that the desired
rendering sizes can be specified in terms of the target device. that is,
for example, one would be able to specify that a line should be rendered
with a width of 2mm on the target device. whereas the current uom
concept allows to define rendering sizes in 'real world' metrics, that
is, one can specify that a line should be rendered as if it was 200m
wide in the real world, and than it is scaled as such.
first, I'd like to gauge the likelihood that such an extension (a patch)
would be accepted into the geotools source code repository. would anyone
have objections to such an extension?
second, I'd like to discuss the way of implementing this. from a Java
implementation perspective, this scaling can be done in the class
UomRescaleStyleVisitor, where it has to be extended to know about the
target devices' dpi. this can easily be done.
the main design question is how to specify such an uom unit in terms of
SLD. currently, the uom value uses some selected units from the
javax.measure packages, with URIs representing various units of
measurement. there are all treated as real-world sizes (see above). this
URIs look like "http://www.opengeospatial.org/se/units/metre"; . to be
able to specify "units in terms of the target device", one has at least
two options:
* introduce a special URI, for example,
http://www.opengeospatial.org/se/units/targetdevice/metre
* add an additional attribute beside 'uom', say 'uom-target', that
could have the values 'real-world' and 'target-device', with the
default being 'real-world' for backwards compatibility
I wonder which approach would be preferred by the geotools community?
best regards,
Akos
PS: all the above assumes that RendererUtilities.getDpi(rendererHints);
would return a realistic DPI value when called from StreamingRenderer. I
wonder where the DPI value comes from - does for example WMS request
supply a realistic DPI value?
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