[Tile-serving] [mod_tile] 32-bit instead of 8-bit PNG output (#64)

[der-stefan]

Rendering meta tiles with mod_tile/renderd always made my hillshade look ugly. This results in the 8 bit PNGs, which Mapnik doesn't rasterize as nice as imagemagick does. The difference can be seen here:
8-bit: ![png256](https://f.cloud.github.com/assets/3618939/1873522/11e41fc2-78bb-11e3-99e0-c4be3c6d901b.png)
32-bit: ![png](https://f.cloud.github.com/assets/3618939/1873520/0494de4c-78bb-11e3-8c2e-2454a3f441ee.png)

Only two lines have to be changed in src/gen_tile.c:
Substitute both "png256" with "png"

There are two possible ways:
- Introduce option in user config file (/usr/local/etc/renderd.conf) for bit depth
- Improve Mapnik. Imagemagick can produce nice looking 8-bit PNGs for example by "convert -type Palette -quality 90 [...]"



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Reply to this email directly or view it on GitHub:
https://github.com/openstreetmap/mod_tile/issues/64
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