On 06/15/2011 10:23 AM, Flo Ledermann wrote: > >> Hi all, >> >> I just noticed a strange behaviour when trying to render 8-Bit PNGs: >> Mapnik seems to stop drawing features when it runs out of colors (or at >> least that is my interpretation so far).
In the end it turned out that it this probably wasn't related to PNG rendering at all but to some rather strange multithreading/IO issues when generating tiles from shapefiles on my machine. I haven't fully investigated the issue yet but I am quite sure it doesn't have to do with PNG output after all. Best, Flo > > OK I just found the documentation on > > http://trac.mapnik.org/wiki/OutputFormats > > I did Google around yesterday but somehow didn't find this. Sorry for > the noise. > > Flo > > >> >> It's best illustrated with the attached tiles - the first was saved as >> 24-Bit PNG, the other one as 8-Bit using >> >> mapnik.Image.save(uri, 'png256') >> >> (in the context of OSM's generate_tiles.py) >> >> I would have expected the latter to be dithered or otherwise distorted, >> but I cannot explain to myself why parts of distinctive layers (roads >> and rivers in the upper part of the image) are omitted, especially given >> that the colors used there are present in the rest of the image. >> >> Can anyone explain to me what is going on here? Or even better give some >> hints or pointers to code how this could be fixed/avoided. >> >> Best, >> >> Flo >> > > _______________________________________________ > Mapnik-users mailing list > [email protected] > https://lists.berlios.de/mailman/listinfo/mapnik-users _______________________________________________ Mapnik-users mailing list [email protected] https://lists.berlios.de/mailman/listinfo/mapnik-users
