[OSM-talk] SVG tiles
80n80n at gmail.com
Mon Apr 21 18:00:07 BST 2008
On Mon, Apr 21, 2008 at 2:33 PM, elvin ibbotson <elvin.ibbotson at 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)
> 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:
> 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 < :-)
> elvin.ibbotson at poco.org.uk
> talk mailing list
> talk at openstreetmap.org
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