Re: Image Server, Shape Layers and Image bounds problem

Paul,

Someone pointed out to me that the layer names are changing in the
printout. It looks like the layer that thinks the projection hasn't
changed is actually right - the projection parameters for that
particular layer are the same (Request 1 and Request 3).

So, the graphics list is getting cleared somehow in the layer between
requests, and the layer doesn't know about it when the identical request
comes in. Is there something else going on that would be clearing the
list in the layer?

- Don

On Tuesday, April 9, 2002, at 09:34 PM, Paul Chisholm wrote:

> Hi Don,
>
> thanks for the reply, it has helped me further investigate the problem.
> The -Ddebug.imageserver did not throw any light on the subject
> but -Ddebug.shape did.
>
> My chunk of code that generates the image is
>
> System.out.println(centre.toString() + "\nScale=" + scale +
> "\nWidth=" + width + "\nHeight="+ height);
> Mercator proj = new Mercator(centre, scale, width, height);
> server.setLayers(layers);
> byte[] bytes = server.getMapImage(proj);
>
> I added a trace statement to print the projection parameters. Here is a
> segment of the trace file.
> *******************************************************
> Request 1
> ---------
> LatLonPoint[lat=-30.0,lon=145.0]
> Scale=1.2E8
> Width=240
> Height=160
>
> OpenMap|ShapeLayer.ShapeWorker.construct(): getting graphics...
> ShapeLayer.computeGraphics(): Dateline is on screen
> OpenMap|ShapeLayer.ShapeWorker.construct(): fetched 70 graphics in 0.07
> seconds
> ShapeLayer.paint(): 70 omg shadow=0,0
> ShapeLayer.paint(): done
>
> Request 2
> ---------
> LatLonPoint[lat=-28.0,lon=135.0]
> Scale=1.2E7
> Width=480
> Height=400
>
> Land|ShapeLayer.ShapeWorker.construct(): getting graphics...
> Land|ShapeLayer.ShapeWorker.construct(): fetched 35 graphics in 0.05
> seconds
> ShapeLayer.paint(): 35 omg shadow=0,0
> ShapeLayer.paint(): done
>
> Request 3
> ---------
> LatLonPoint[lat=-30.0,lon=145.0]
> Scale=1.2E8
> Width=240
> Height=160
>
> ShapeLayer: projection not different, returning...
> OpenMap|ShapeLayer.ShapeWorker.construct(): getting graphics...
> ShapeLayer.computeGraphics(): Dateline is on screen
> OpenMap|ShapeLayer.ShapeWorker.construct(): fetched 70 graphics in 0.03
> seconds
>
> Request 4
> ---------
> LatLonPoint[lat=-30.0,lon=145.0]
> Scale=1.2E8
> Width=240
> Height=160
>
> OpenMap|ShapeLayer.ShapeWorker.construct(): getting graphics...
> ShapeLayer.computeGraphics(): Dateline is on screen
> OpenMap|ShapeLayer.ShapeWorker.construct(): fetched 70 graphics in 0.03
> seconds
> ShapeLayer.paint(): 70 omg shadow=0,0
> ShapeLayer.paint(): done
> *******************************************
>
> The interesting one is request 3. In particular the line
>
> ShapeLayer: projection not different, returning...
>
> It looks like the system thinks the projection is unchanged and doesnt
> regenerate the shape layer. However from the trace the projection must
> have
> changed since the parameters are different. This is the request in
> which the
> shape layer is missing from the image. I had a quick look at the code
> but I
> need to spend more time on it to make sense of it. As a test I created
> MyShapeLayer which over-rides projectionChanged in ShapeLayer with
>
> public void projectionChanged(ProjectionEvent ev) {
>
> Projection newProj = ev.getProjection();
> String newPID = newProj.getProjectionID();
> projection = newProj;
> projID = newPID;
>
> doPrepare();
> }
>
> I have just removed the test for the projection change. Using
> MyShapeLayer
> the problem disappears.
>
> Paul
>
> ----- Original Message -----
> From: "Don Dietrick" <dietrick@bbn.com>
> To: "Paul Chisholm" <paulch@bigpond.com>
> Cc: <openmap-users@bbn.com>
> Sent: Wednesday, April 10, 2002 12:54 AM
> Subject: Re: Image Server, Shape Layers and Image bounds problem
>
>
> Paul,
>
> When the shape layer is missing, is it even being asked for any
> graphics? You could set a -Ddebug.shape command line to see if it is
> getting pinged. Actually, you could use -Ddebug.imageserver for better
> messages about what the image server is doing with what layers.
>
> I haven't seen this behavior. The ImageServer should be calling the
> layer's ProjectionPainter method (renderDataForProjection()), so the
> layer shouldn't be reacting differently to any one projection over
> another - i.e. what you are expecting to happen should be happening.
>
> - Don
>
> On Tuesday, April 9, 2002, at 01:37 AM, Paul Chisholm wrote:
>
>> Hi,
>>
>> I have a server that uses OpenMap to generate JPEG files and it is
>> exhibiting some strange behaviour. The images are created via the
>> ImageServer class. Two different types of image are generated, one
>> essentially a large scale version of the other. Both consist of a shape
>> layer and a few other (non Shape) layers. What happens is:
>>
>> - request first image, ok
>> - request second image, shape layer missing
>> - request first image, shape layer missing
>> - request second image, shape layer missing
>> - request second image, ok
>> - request second image, ok
>> - request first image, shape layer missing
>> etc
>>
>> The pattern is that each time I change between maps the shape layer is
>> missing from the image. However, a subsequent request for the same map
>> includes the shape layer.
>>
>> I experimented with various parameters and eventually found that the
>> cause of the missing shape layer is due to the change in dimensions of
>> the image. That is, when there is a change to either <width> or
>> <height> in the following (wrt the previous request) the shape layer is
>> missing from the image (95% of the time).
>>
>> server.setLayers(<layers>);
>> Mercator proj = new Mercator(<centre>, <scale>, <width>,
>> <height>);
>> byte[] bytes = server.getMapImage(proj);
>>
>> Changing <centre>, <scale> or <layers> causes no problem.
>>
>> I am using OpenMap 4.4.2 on Windows NT 4 (SP6). Anyone know of any
>> reason why this behaviour occurs, or how I might be configuring
>> something incorrectly to induce the behaviour.
>>
>> Thanks,
>> Paul Chisholm
>>

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Don Dietrick, BBN Technologies, dietrick@bbn.com
10 Moulton Street, Cambridge, MA 02138
617-873-3031 [fax]-2794
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>

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