[OSM-dev] PNG type for Mapnik map

[Christopher Schmidt]

On Wed, Dec 19, 2007 at 12:37:54PM +0000, Robert (Jamie) Munro wrote:
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> Jochen Topf wrote:
> > Hi!
> > 
> > http://svn.openstreetmap.org/applications/rendering/mapnik/generate_tiles.py
> > uses a call to the external 'convert' program to reduce the number of colors
> > for tiles rendered by Mapnik to 255. Since version r571 Mapnik supports
> > writing to 8 bit palette PNGs. Palette PNGs are generally smaller than
> > normal PNGs.
> > 
> > Is there any reason NOT to change the code to use Mapniks function to
> > write out the image directly as 8bit paletted PNG, make the images
> > smaller and save the call to 'convert'? (If nobody comes up with a
> > reason, I'll change the code.)
> 
> AFAIK, the main reason the feature was added to mapnik was that /we/
> needed it because the external convert was really slow (about the same
> amount of time as the whole rest of the render).
> 
> So no, there is no reason not to change the code. Please do & make
> mapnik run at twice the speed. Also, if you can make mapnik render
> on-demand first, and only render the backlog when it's not busy, that
> would probably be a great improvement.

You seem to be confusing generate_tiles.py with the rendering setup that
is used on the main mapnik server. I don't think they're related.

Also, you seem to think that rendering on demand is actually plausible
under normal load -- it's not.

This is a tool for developers, which (unless I'm crazy, which is
possible) is almost totally unrelated to the production tile generation
code.

Regards,
-- 
Christopher Schmidt
MetaCarta