Hi,
I do not know TTF image format but if is behaves like TIFF then I can have a
try.
1) Build overviews for the big image. Gdal program gdaladdo can make it for
the image formats it is supporting. It means in practise that high resolution
image is subsampled to bigger pixel sizes. Overviews can be internal
(subsampled, so called pyramid layers are written inside of the image file) ot
they can be external. Program supporting overviews is picking the right
resolution level automatically for rendering. I do not know if Mapnik supports
overviews but it is possible because it is using gdal.
2) Make a static subsampled image(s) to be used in Mapnik rendering when zoomed
out. Gdal_translate can make those.
3) Build tiles for the slippy map directly with MapTiler program
(http://maptiler.org). It is a nice piece of software and worth a try at least.
-Jukka Rahkonen-
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Lähettäjä: [email protected]
[mailto:[email protected]] Puolesta Alireza Kashian
Lähetetty: 14. toukokuuta 2009 11:24
Vastaanottaja: [email protected]
Aihe: [Mapnik-users] Rendering satellite imagery as a layer for
hybridview in mapnik
Hi.
My last question about PNG compression was answered perfectly. thanks
to all responders.
One of the things we are trapped in is satellite view for our slippy
map.( we want to have hybrid)
We got the files from quickbird satellite in TTF (GeoRefrenced). like
700 Square Km.
The whole city is like 18 Gigabyte in Size. I mean the size of single
colorful TTF file.
We tested mapnik against that big TTF file and used the GeoRefrenced
TTF as a source for mapnik layer.
The problem is the size of TTF when mapnik wants to make a tile in a
specific zoom. We have 8 GIG of ram in Debian, but still we are in lack of
memory.
I think mapnik tries to open up the TTF file, but since it is so much
big, it fails. it is logical.
The solution would be slicing the TTF into smaller files. We tried even
with 1 GIG files, but still fails.
so my question is that : What is the technique for rendering satellite
imagery when you handle large ttf files. If the answer is slicing, then what
happens to edges between two tiles when one part is in TTF1 and the second part
is in TTF2...how can we tell mapnik to use which TTF file...things are a bit
vague..how many slices we should make !
thanks
Alireza
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