Yup! Osmarender seems to produce SVG, and I guess SVG is an
intermediate stage in producing the bitmap [EMAIL PROTECTED] tiles, but
what I am suggesting should be considered is a server that would
deliver tiles in SVG format instead of/as an alternative to bitmap
tiles. Could this be done simply (as if anything was ever simple :-)
caching the SVG between running Osmarender and converting SVG to
bitmaps?
On 21 Apr 2008, at 18:00, 80n wrote:
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]
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