[Phpmyadmin-devel] Prototype implementation - Visualizing GIS data

[Madhura Jayaratne]

On Wed, May 11, 2011 at 4:37 AM, Piotr Przybylski <piotr.prz at gmail.com>wrote:

> 2011/5/10 Madhura Jayaratne <madhura.cj at gmail.com>:
> >
> >
> > On Tue, May 10, 2011 at 11:51 PM, Madhura Jayaratne <
> madhura.cj at gmail.com>
> > wrote:
> >>
> >>
> >> On Tue, May 10, 2011 at 11:39 PM, Marc Delisle <marc at infomarc.info>
> wrote:
> >>>
> >>> Madhura Jayaratne a écrit :
> >>> > Hi all,
> >>> >
> >>> > During the past few days I was playing around with the code to do a
> >>> > test
> >>> > implementation for GIS data visualization. Now I have pushed it to my
> >>> > repo and I would like to hear you comments about it. You can check it
> >>> > out at [1].
> >>> >
> >>> > Currently it does the following
> >>> > 1. 'Visualize GIS data' link is displayed in 'Query results options'
> >>> > pane ONLY for query results that has atleast one geometric column.
> >>> > 2. If there are more than one geometric columns in the results, the
> >>> > user
> >>> > can chose which column to be used for th visualization
> >>> > 3. You chose out of non-geometric columns a label column, which is
> used
> >>> > for tooltips.
> >>> > 4. Also, try zooming and panning.
> >>> >
> >>> > I created a database with geometric data (database: opengis), so it
> >>> > would be easy for you to test the above. In case database server has
> >>> > reset by the time you login and you can't find the database, I have
> >>> > also
> >>> > attached the sql file here.
> >>> >
> >>>
> >>> Madhura,
> >>> no file was attached but I suggest opening a patch artifact and
> >>> attaching your file there.
> >>>
> >> Ooops!!
> >> I opened a patch artifact and attached the sql file there. You can find
> it
> >> at [1]
> >>
> >
> > One problem I encountered during the implementation is that flot does not
> > support drawing polygons with voids inside them. I had to draw another
> > polygon with its fill color set to background color in order to pretend
> the
> > void and i'm not vary happy with that :(
> > However reading the SVG specification I didn't find it to
> support polygons
> > with voids either [1]. I'm wondering what to do about that.
>
> What do you mean by "polygons with voids"? It you mean that you need a
> polygon's outline, use <polyline> with the first point repeated at the
> end, this should do the trick.
>
>
In a polygon object like
POLYGON((35 10,10 20,15 40,45 45,35 10),(20 30,35 35,30 20,20 30))
(35 10,10 20,15 40,45 45,35 10) refers to the outer ring while (20 30,35
35,30 20,20 30) refers to the inner ring.
A polygon has exactly one outer ring and zero or more inner rings.

When visualizing the polygon, area under the outer ring, but not under any
inner rings should be colored.

So the hack I have used is, I have drawn the outer ring and on top of that
drawn the inner rings with the background color. You can find a polygon
which has inner rings in the dataset I have uploaded to the demo. (database:
opengis, table:gis_all)

-- 
Thanks and Regards,

Madhura Jayaratne
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