[Geoserver-users] Black areas in Silverlight Map Control

GeoServer GeoServer User
1

If you are using the Silverlight map control with GeoWebCache, you might get black areas.

I’ve put together a blog post that explains this and the fix:

http://rogerbedell.blogspot.com/2009/05/black-areas-in-silverlight-map-control.html

Roger

2

This suggests that SilverLight can't handle transparent 8 bit PNGs. The following test would nail that down (or not)

What happens if you use format=image/png8 for the entire layer ? You can append it to the gmaps request to GWC.

-Arne

Roger Bedell wrote:

If you are using the Silverlight map control with GeoWebCache, you might get black areas.

I've put together a blog post that explains this and the fix:

http://rogerbedell.blogspot.com/2009/05/black-areas-in-silverlight-map-control.html

Roger

--
Arne Kepp
OpenGeo - http://opengeo.org
Expert service straight from the developers

3

Arne, I just tried that, and I don't think that is the problem, as everything still seems to work fine using png8.
Here is a sample tile request, I don't know if it is out of bounds or not, but I tried.

http://ogi.state.ok.us:8080/geoserver/gwc/service/gmaps?layers=ogi:okcounties&zoom=8&x=39&y=101&format=image/png8

I got this from the GWC docs, http://geoserver.org/display/GEOSDOC/GeoServer+GeoWebCache+Configuration

<!-- This defines the extent of your data and prevents GeoWebCache from
             requesting blank tiles from the backend, thereby saving storage and
             responding faster. -->
        <dataBounds>
          <coords>
            <double>-103.87</double>
            <double>44.37</double>
            <double>-103.62</double>
            <double>44.50</double>
          </coords>
        </dataBounds>

So, does GWC return a blank transparent PNG8 when out of bounds? or nothing at all? Perhaps Silverlight just doesn't like a blank, transparent PNG8?

Roger

--------------------------------------------------
From: "Arne Kepp" <ak@anonymised.com>
Sent: Tuesday, May 19, 2009 12:01 PM
To: "Roger Bedell" <roger@anonymised.com>
Cc: <geoserver-users@lists.sourceforge.net>
Subject: Re: [Geoserver-users] Black areas in Silverlight Map Control

This suggests that SilverLight can't handle transparent 8 bit PNGs. The
following test would nail that down (or not)

What happens if you use format=image/png8 for the entire layer ? You can
append it to the gmaps request to GWC.

-Arne

Roger Bedell wrote:

If you are using the Silverlight map control with GeoWebCache, you might get black areas.

I've put together a blog post that explains this and the fix:

http://rogerbedell.blogspot.com/2009/05/black-areas-in-silverlight-map-control.html

Roger

--
Arne Kepp
OpenGeo - http://opengeo.org
Expert service straight from the developers

4

Ok, not sure then, but was worth a try :slight_smile:

Out bounds -> optimized transparent PNG (only 129 bytes)

The request you show is indeed out of bounds, if you use Firebug or curl you can see the HTTP response headers: geowebcache-message: gridX (39) must be at least 54

-Arne

Roger Bedell wrote:

Arne, I just tried that, and I don't think that is the problem, as everything still seems to work fine using png8.
Here is a sample tile request, I don't know if it is out of bounds or not, but I tried.

http://ogi.state.ok.us:8080/geoserver/gwc/service/gmaps?layers=ogi:okcounties&zoom=8&x=39&y=101&format=image/png8

I got this from the GWC docs, http://geoserver.org/display/GEOSDOC/GeoServer+GeoWebCache+Configuration

<!-- This defines the extent of your data and prevents GeoWebCache from
             requesting blank tiles from the backend, thereby saving storage and
             responding faster. -->
        <dataBounds>
          <coords>
            <double>-103.87</double>
            <double>44.37</double>
            <double>-103.62</double>
            <double>44.50</double>
          </coords>
        </dataBounds>

So, does GWC return a blank transparent PNG8 when out of bounds? or nothing at all? Perhaps Silverlight just doesn't like a blank, transparent PNG8?

Roger

--------------------------------------------------
From: "Arne Kepp" <ak@anonymised.com>
Sent: Tuesday, May 19, 2009 12:01 PM
To: "Roger Bedell" <roger@anonymised.com>
Cc: <geoserver-users@lists.sourceforge.net>
Subject: Re: [Geoserver-users] Black areas in Silverlight Map Control

This suggests that SilverLight can't handle transparent 8 bit PNGs. The
following test would nail that down (or not)

What happens if you use format=image/png8 for the entire layer ? You can
append it to the gmaps request to GWC.

-Arne

Roger Bedell wrote:
    

If you are using the Silverlight map control with GeoWebCache, you might get black areas.

I've put together a blog post that explains this and the fix:

http://rogerbedell.blogspot.com/2009/05/black-areas-in-silverlight-map-control.html

Roger
      

--
Arne Kepp
OpenGeo - http://opengeo.org
Expert service straight from the developers

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--
Arne Kepp
OpenGeo - http://opengeo.org
Expert service straight from the developers