[Tilesathome] less inkscape runs

[Dirk-Lüder Kreie]

spaetz schrieb:
> On Thu, Aug 21, 2008 at 11:17:05AM +0200, Dirk-L?der Kreie wrote:
> 
>> You are aware that the stripes are not equal in height, which is precisely 
>> why there are 32 calls at z 17 (instead of 1024 as it used to be, BTW)
> 
> They aren't? Isn't it always 256px height stripes? I see there is a reason why I haven't dared touching the main rendering functions yet. :-)

If you remember the white borders Batik error, that one resulted because 
the svg is not exported 1:1 but slightly squished (one way or the 
other). this squishing is dependent on latitude, so the stripe height in 
the PNG will always be the same (256px), but not in the svg source.

This works around the osmarender projection bug.

I made some tests with a perl program that gave me the arithmetic and 
projected middle-line of several tiles, and I found the maxError to be 
around 0.6px for z12/13, and 0.03px for z16/17 (PNG tile pixels, that 
is), so we could use the splitImage function from tilesPipeAtHome to 
enhance our existing splitImageX to handle the entire svg area at once, 
and just live with a bit more than half a pixel inaccuracy at z12/13.

However this will *not* work for caption rendering, as the error at z6 
is tens of pixels.

-- 

Dirk-Lüder "Deelkar" Kreie
Bremen - 53.0952°N 8.8652°E

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 260 bytes
Desc: OpenPGP digital signature
URL: <http://lists.openstreetmap.org/pipermail/tilesathome/attachments/20080821/def56c48/attachment.pgp>