Created attachment 50024 [details]
Screenshot illustrating the problem

Version:           unspecified (using KDE 4.5.0) 
OS:                Linux

Even when using the Mercator projection for OpenStreetMap (which should not result in any geometric transformation of tiles), Marble displays a blurred map as if the tiles were geometrically transformed or resampled due to zoom level mismatches. An attached screenshot demonstrates the web-based Mapnik rendering side-by-side with Marble's rendering at a comparable zoom level.

Reproducible: Always

Steps to Reproduce:
Select Openstreetmap display with Mercator projection in Marble, compare the rendering to a similar zoom/area rendered by Mapnik at openstreetmap.org

Actual Results:  
Marble's rendering is consistently more blurred than the original Mapnik tiles.

Expected Results:  
Marble should try its best to display raster tiles pixel-exactly where possible (maybe by snapping to the optimal zoom levels).

OS: Linux (x86_64) release 2.6.35-gentoo-alchark-u3s
Compiler: x86_64-pc-linux-gnu-gcc