[Tilesathome] color-reducing

[Kai Krueger]

Dirk-Lüder Kreie wrote:
> Jannis Achstetter schrieb:
>> Hello list,
>>
>> of course I support the idea to reduce the colors of a tile but can we 
>> use a little more colors than now?
>> the reason I'm writing is this:
>> http://informationfreeway.org/?lat=49.97776785345019&lon=9.148058101976218&zoom=17&layers=B000F000F 
>>
>>
>> Have a look at the traffic-lights and the pharmacy-icons. Adding some 
>> more colors or adjusting the icons might help here.
> 
> Thanks for spotting, increased colour depth to 256 colours.

Hmm this seems to really be quite a difficult example. Even in the 256 
colour case, the traffic lights don't look good. I have added an example 
tile from that to the wiki page. 
(http://wiki.openstreetmap.org/index.php/Tiles%40home/ColorPallet)

I could imagine that the following is happening. The traffic lights only 
have a very few pixels, so not enough "weight" for the algorithm to 
conserve their colours. Yet, because they form a contiguous region with 
high visual saliency, the deviation is well perceivable. So I guess 
these symbols will cause automated algorithms more problems than the 
simple linear features such as roads.

Thanks for the good test case.

Kai

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