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Re: [udig-devel] SLD vs zoom specific widths
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At 12:31 PM 4/2/2005, Jody Garnett wrote:
Matthias basler (JIRA) wrote:
I styled the rivers example shape file with a border (width 2) and fill
color.
When zooming in and out I find that the rendered border width does not
change.
When I zoom out quite a bit the whole rivers are shown as border only because
their "interiour to edge ratio" becomes quite small.
This is a general issue: Should the border width (and icon size, text
size etc) be scaled according to zoom level or not?
Pro:
- A user of analogous maps would expect that the overall maplayout does
not change, no matter what zoom level is chosen. That is, a river with a
border of ~1/10th of the line width is pained this way on all scales.
This is relevant for printing!
Contra:
- The OGC SLD probably (I don't know!) handles styles as
scale-independent - so "2 points" is always the same width, no matter
what scale is chosen.
This is true for now. There is support for scale dependant rules, i.e. you
can switch from one styling rule to another depending on the current scale,
but you can't do something that changes continously.
Two changes are on the cards, the fist is an Environment Variable
expression which will evaluate to the current map scale. Partial support
for this is already implemented in GeoTools in anticipation of the next
spec. The second is more elegant but more speculative (its not been
debated much within the SLD revision group) it will allow units ('pixels',
'meters' ...) to be used for sizes, widths etc.
James
