On Mon, Apr 21, 2008 at 2:33 PM, elvin ibbotson <[EMAIL PROTECTED]> wrote:
> poco.org.uk > > I have developed a mobile-phone Java app (called 'mom') to navigate OSM > maps and save GPX tracks (amongst other things) which will soon be out there > for people to download. It uses mapnick PNG tiles at 5 of OSM's scales (3, > 6, 9, 12 & 15) which look nice but are quite big files to download to a > phone (typically 12kB-15kB for scale 15) so take a significant amount of > time and eat into a user's data allowance to fetch. > > I considered using the compact binary downloads aimed at mobile apps, but > this is raw data and the graphics limitations of mobile Java mean the maps > drawn from it would not look very pretty. > > I am fairly ignorant of OSM data structures and back-room software but I > understand SVG is used in producing bitmap tiles. As I understand it, the > idea of SVG is not only to give nice, scalable, graphics, but to do so using > smaller file/download sizes than bitmaps. Many/most of the newest mobile > phones are able to draw SVG graphics in Java, as are browsers, and desktop > Java will soon include SVG graphics, so it looks to me like the way forward. > If tiles were available as SVG I am sure it would be relatively easy to > substitute them for bitmap tiles in slippy maps or apps like mine. Not only > would downloads be faster but a smaller range of scales would be needed, > with the same data set and appearance being used for a range of scales and > scaling of the SVG image used for intermediate (or infinitely adjustable) > scales. > > I had been intending to get round to mailing this list enquiring if SVG > downloads were possible/available when the Export tab appeared. My initial > delight** was slightly diminished when I exported a map in two formats - SVG > and PNG - and found the SVG version was 340kB while the PNG file was 132kB. > A glance at the SVG data suggests that text is actually drawn (sometimes > more than once (for background then again for the text itself) using long, > elaborate paths and shape definitions of every character at every > orientation and size, rather than just using the SVG text element!!! I > suspect it also incorporates bitmap images as icons rather than using SVG > definitions. I think SVG is the way forward, but not if the file sizes end > up almost three times bigger than bitmaps! > Take a look at Osmarender. This creates proper SVG. Details here: http://wiki.openstreetmap.org/index.php/Osmarender > > I suggest that, if has not already been done and is hidden somewhere I > haven't looked, that a server should be dedicated to scalable map tiles > using a compact and efficient implementation of SVG coding. > > **Hats off to those involved, by the way < :-) > > [EMAIL PROTECTED] > > > > > > > _______________________________________________ > talk mailing list > talk@openstreetmap.org > http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk > >
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