[OSM-dev] NOT-saving empty Mapnik tiles

Oliver Tonnhofer olt at omniscale.de
Mon Aug 15 22:30:39 BST 2011


On 15.08.2011, at 23:15, Igor Podolskiy wrote:
>> No, it stops as soon as it sees the second color (for getcolors(1))...
> ummm, my gut says there isn't a second color in a single-color image :)

Well, that's true for actual single color images, but not for regular tiles.

>> and Mapniks tostring() and PILs fromstring() are just a memory copy. So this will also be fast. Of course, you need PIL as a dependency.
> Don't know about Mapnik, but since I had the PIL sources open anyway, I looked it up. PILs fromstring() is a bit more involved than a memory copy. It actually has a cyclomatic complexity of three. Of course, it most probably _is_ quite fast so that you can't tell it from a memory copy for most practical purposes.

It's 28x faster on my system for a transparent tile.

`Image.frombuffer('RGBA', (256, 256), img, 'raw').getcolors(1)` takes 0.18ms and 
`is_tranparent(img)` 5.2ms

Regards,
Oliver

-- 
Oliver Tonnhofer    | Omniscale GmbH & Co KG    | http://omniscale.de
http://mapproxy.org | https://bitbucket.org/olt | @oltonn







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