[josm-dev] Automatic tiles downloading in WMSPlugin
petr.dlouhy at email.cz
Fri Aug 29 18:23:31 BST 2008
On Fri, 29 Aug 2008 18:44:52 +0200, Bodo Meissner <bodo at bodo-m.de> wrote:
> Petr Dlouhý wrote on 28.08.2008 15:51:
>> Ok, I implemented save and load (bud I doubt, if it is usefull).
> I think loading the images from a file must prevent the plugin from
> downloading the images again. It might even be useful to optionally
> switch off the automatic downloading when I know I already have the area
> i'm interested in.
Ok, I will implement "stop downloading" and "start downloading" in the
right-click menu of WMS layer and when loaded from file, the downloading
will be stopped. Good tip.
>> I also
>> implemented grabber choosing through getGrabber(), but to get
>> working, it needs to be rewriten to thread support.
> Does the plugin download several tiles at the same time? I hope this
> does not place too much load on the servers.
> Even with the old WMS plugin the Landsat WMS server was sometimes very
> slow or down because of overload. If the load gets higher this might
> annoy the people who run a WMS server.
Hm, yes. The fact is, that thread support is necessary, to be able to work
when downloading the tiles. Maybe some synchronization can be done between
threads to prevent opening more than one connection in same time.
>> The new version could be downloaded from:
> I will be in holidays for the next two weeks. That's why I don't have
> time to test it now.
>> I don't like waiting before the tiles get loaded, it would be very
> If there was a configurable delay you could set the delay to 0 to get
> the tiles downloaded immediately. I, personally, would set the delay to
> something like 2 seconds
>> The tiles are downloaded only if it's zoomed enough, so if you want to
>> look around without downloading new tiles, then just zoom out a little.
>> found that very intuitive.
> I do not want to look around but move the display to the next place to
> work on. When I stop at some place only to release the mouse button,
> move the mouse to the other end of the screen and then press the button
> again, there is no need to start downloading this tile.
It is downloading even when you are just moving with the screen now.
Probably it souldn't be downloaded, when moving. When I'm making a long
way (several kilometers), I want to start with the tiles as soon as
possible. I will think it through, I am not sure, if I can make the dellay
easily. Maybe this could be done after commiting actual changes to SVN.
> I think I had to zoom out very much to stop the automatic downloading.
This is configurable in the sources, maybe it could be placed in the
> Regarding zoom and automatic downloading I see a different problem.
> I know one WMS server that returns white images if I zoomed in too much.
> Normally I zoom out enough before manually downloading images, then I
> zoom in to draw or check objects. In this zoom level I do not want any
> downloads because it would fill the area with white images. To prevent
> this problem with your plugin I would need a server specific limit for
> the zoom level or image resolution. When I have zoomed in too much the
> plugin should either not download any tiles or download tiles with the
> maximum resolution available for this server.
No it don't work this way. It is downloading all tiles in one zoom level
(it is best to do it this way, because some WMS servers give different
image depending on zoom level), which is set when the WMS is activated,
and the zoom level can be reset by clicking on relevant item in WMS menu.
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