OpenStreetMap
I stumbled across optipng (for Linux) recently, and wondered whether it would be worth running this on the OSM tiles (or rather, incorporating the algorithm into newly generated ones).
It seems to get maybe 25% size reduction on "empty" tiles (ocean, fields) but only 2-3% on "busy" urban tiles.
Discussion
Ulasan andrewpmk terhadap 11 Ogos 2009 pada 00:18
It would probably take far too much CPU power to be worth running on the tile server.
Ulasan Falcorian terhadap 11 Ogos 2009 pada 00:51
And of course optipng isn't the only compression program, pngout for example generally gets smaller files at the cost of more processing time.
Ulasan adaviel terhadap 11 Ogos 2009 pada 01:03
I remember I used to get significant reduction in GIFs by reducing the palette size, before everyone had broadband. With people getting images over cell data networks (and maybe paying per kb) there may be some point to it again.
On a related topic, I forget whether I saw it on OSM or Maemo Mapper - is there any scheme to save downloads by redirecting all requests for "empty blue tile" to the same URL ?
Ulasan Firefishy terhadap 14 Ogos 2009 pada 08:56
The OSM Mapnik tiles are 256 colour PNGs to improve their size.
The tile server is CPU bound and currently bandwidth usage is not a problem.
Ulasan adaviel terhadap 15 Ogos 2009 pada 03:18
I tried pngout. Much slower than optipng, at least on the maybe 1.5Mpixel image I used.
I was thinking about bandwidth on mobile clients, not the server.