On Tue, 2006-05-09 at 17:02 +0200, Jody Garnett wrote: > In that case we will need to ask Richard to implement a different plugin > for the InfoTool for each renderer he creates. Not fun but possible. I > did think he ended up making a 2x2 reference image and selecting the > first pixel (after having a few WMS fail on a 1x1 image reference image.
Err.. I made a couple experiments with this, but I didn't ever think it was really feasible. I think the goal was to be able to provide a buffer around a point clicked, or provide support for bbox-enabled GetFeatureInfo requests (WMS spec says you can only use point requests). Since the info tool in uDig is point based, I presume that the desire is to provide a buffer? Paul is right in that shrinking the image a bit would be closer to the desired effect. If we shrink the image to 3x3 and ask for one pixel, we are going to get 1/9 of the screen back (and possibly the wrong section too). So I think we should default back to just using the standard method of doing it (ie. let the WMS provide tolerance if it wishes). We could add a preference option to enable a buffer around the point and then use the voodoo code, but I don't think it should be a default. I'll see if I can fix this on Thursday morning, before the RC release. Richard > Jody > > > > I think the problem with this approach, as now demonstrated, is that > > it doesn't work :) It might take something a little more "arbitrary", > > like a pretend image of "about 300 pixels in size" with the click > > point in the "middle of that image" to get a correct-seeming answer. > > Sending back a one-pixel map with a click "on the pixel" is begging to > > hit corner cases in the WMS server side code. > > > > On 5-Sep-06, at 12:29 AM, Jody Garnett wrote: > > > >> Ah, interesting question ... because of a difference between what we > >> display and what we requested from the WMS. > >> - often we will have to make several requests and tile content onto > >> the screen in WMS happy chunks, > >> - or we will need to make slightly larger requests and resample them > >> onto the screen (as mentioned previously). > >> > >> It was just easier to back project a pixel and use it to make a > >> request in the correct location once, rather then trying to reverse > >> several rendering process es to exactly match the original request > >> (aka the approach we used for uDig 0.8). > >> > >> Cheers, > >> Jody > >>> Hi Jody, > >>> > >>> why did you end up changing the BBOX and width/height client-side? > >>> Why not leave it up to the WMS server like Gaia does? > >>> > >>> Best regards, > >>> Bart > >>> > >>> Jody Garnett schreef: > >>>> Indeed, we eventually figured out that WMS getInfo is considered a > >>>> check in the center of a single pixel. > >>>> > >>>> Thinking, > >>>> > >>>> Richard for a while we forced the renderers to leave us a hook so > >>>> we could make our info request, is there any way we can ask the WMS > >>>> renderers to leave some hints on the layer blackboard about the > >>>> image rendered? The same plugin making the rendering contribution > >>>> can provide the hint ... > >>>> > >>>> Jody > >>>>> Hi Jody, > >>>>> > >>>>> the projections I am trying are both supported by the WMS. > >>>>> > >>>>> Unfortunately I have no Java hosting, but it's a simple shapefile > >>>>> which can be set up with Geoserver. I am using 1.4. > >>>>> > >>>>> The shapefile can be found here (200 Kb, native projection > >>>>> EPSG:28992, uDIG set to RD / New projection): > >>>>> > >>>>> http://www.osgis.nl/lausanne/nl-prov.zip > >>>>> > >>>>> An example request which uDIG is fyring off is (this request is > >>>>> really strange since the BBOX is not the BBOX of the map image > >>>>> shown anymore! and X and Y are always 1): > >>>>> > >>>>> /geoserver/wms?Y=1&X=1&SERVICE=WMS&INFO_FORMAT=text/html&LAYERS=ogctestbed:nl-prov&FORMAT=image/png&HEIGHT=3&REQUEST=GetFeatureInfo&WIDTH=3&BBOX=188907.50415179788,391802.21024004533,192453.4125990071,395348.1186872545&SRS=EPSG:28992&QUERY_LAYERS=ogctestbed%3Anl-prov&VERSION=1.1.1 > >>>>> > >>>>> HTTP/1.1" 200 447 > >>>>> > >>>>> Thanks in advance. > >>>>> > >>>>> Best regards, > >>>>> Bart > >>>>> > >>>>> Jody Garnett schreef: > >>>>>> Good question, it makes a direct call when able to make a direct > >>>>>> rendering of the WMS image (ie udig is using a coordinate system > >>>>>> supported by the WMS). In rare cases it may have to resample the > >>>>>> image onto the screen (making up for lack of WMS projections), we > >>>>>> could check that we back project the query into the coordinate > >>>>>> space of the original image... but as I recall I wrote this one > >>>>>> and went to some trouble to get it right. > >>>>>> > >>>>>> Can you point us at a service illustrating the problem, perhaps > >>>>>> in a jira report. > >>>>>> Jody > >>>>>>> Hi list, > >>>>>>> > >>>>>>> how accurate is uDIG with respect to GetFeatureInfo? > >>>>>>> > >>>>>>> I have tried it against 2 WMS's, Geoserver and Deegree, and at > >>>>>>> the borders of provinces, a lot of times the wrong element is > >>>>>>> returned. Ofcourse this could also be due to the WMS's. > >>>>>>> > >>>>>>> So I checked Gaia, and using Gaia it is very accurate for > >>>>>>> Geoserver, so I am assuming it is a uDIG problem. > >>>>>>> > >>>>>>> Any input appreciated. > >>>>>>> > >>>>>>> Best regards, > >>>>>>> Bart > >>>>>>> > >>>>>> > >>>>>> > >>>>>> _______________________________________________ > >>>>>> User-friendly Desktop Internet GIS (uDig) > >>>>>> http://udig.refractions.net > >>>>>> http://lists.refractions.net/mailman/listinfo/udig-devel > >>>>>> > >>>>>> > >>>>> > >>>>> > >>>> > >>>> > >>>> _______________________________________________ > >>>> User-friendly Desktop Internet GIS (uDig) > >>>> http://udig.refractions.net > >>>> http://lists.refractions.net/mailman/listinfo/udig-devel > >>>> > >>>> > >>> > >>> > >> > >> > >> _______________________________________________ > >> User-friendly Desktop Internet GIS (uDig) > >> http://udig.refractions.net > >> http://lists.refractions.net/mailman/listinfo/udig-devel > > > > _______________________________________________ > > User-friendly Desktop Internet GIS (uDig) > > http://udig.refractions.net > > http://lists.refractions.net/mailman/listinfo/udig-devel > > > _______________________________________________ > User-friendly Desktop Internet GIS (uDig) > http://udig.refractions.net > http://lists.refractions.net/mailman/listinfo/udig-devel _______________________________________________ User-friendly Desktop Internet GIS (uDig) http://udig.refractions.net http://lists.refractions.net/mailman/listinfo/udig-devel
