Hi Rainer
>
> I know which scale and projection to use to get best results for TMS
> maps (a power of 2 scale based on 1.1943285465 for zoom level 17 and
> EPSG:3857/WGS84 Pseudo Mercator) but I can not evaluate the impact of
> any code modification on other map types. In QLGT there is the "square
> zoom" option for WMS maps. Maybe a similar option could be used in QMS
> to switch between a "logarithmic" and a "square" scale?
I avoided such an option so far to keep it simple. There might be another
solution. The trick is to pick the
best TMS level to be scaled for the current selected scale. The code picks the
closest level and uses that
silly correction factor. It might be much better to do that with a conversion
table. By that you can fine tune
the selection. I can't tell if that really helps. My interest in online maps is
pretty low. But you can give it a try.
Or add an issue, so someone else might get interested.
>
>
> BTW, I think there is a bug in IMap::drawTile:
>
> qreal w = ceil ( sqrt(dx1*dx1 + dy1*dy1));
>
> For dx1=-256 and dy1=0 ceil returns 257 which causes a 256x256 tile to
> be rescaled by 1 pixel blurring it unnecessarily. Maybe replacing "ceil"
> by "round" would be better. Of course this effect only occurs with a TMS
> specific scale.
That is on purpose. With the common map view all maps have to be reprojected.
If their projection type is
the same as the projection of the view, it's a simple rescaling and offset. But
if the projection type differs it
is much more. The reprojection would be something like a key stone with curved
lines. Of course it is to
complicated to do a real reprojection on-the-fly. Map rendering would take much
longer.
That is why I reduce to reprojection to scale, offset and rotation. That works
pretty well. But on certain
scale factors it's not perfect and there is a one pixel gap. This is really
annoying. That is why I use ceiling. I
never had the feeling this really influences the quality of the tile. Probably
the scaling algorithm simply
doubles a row/column of pixels. But sometimes you see a small mismatch of the
border tiles. And this is
the reason for the square pattern in DEM overlays that can be observed a
certain scales, too. But from my
point of view this is all visually more acceptable than a gap between tiles.
Oliver
>
> Best reagrds
> Rainer
>
>
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