[MapProxy] Image quality problem for 8 bit paletted png, ragged lines

[Anne Blankert]

On 11-4-2012 10:25, Oliver Tonnhofer wrote:
> Hi Anne,
>
> On 05.04.2012, at 17:51, Anne Blankert wrote:
>> I am having a (minor) problem with image quality. Cached lines are much more ragged than the original lines. Resolution and projection of source and cache are identical. I found a work-around (meta_buffer:0, meta_size[1,1]), but I think it would be better if the work- around would not be necessary?
>> Visual
>> 1. cached 256x256 png image: http://research.geodan.nl/edugis/images/raggedlines.png
>> 2. wms original 1184x1184 png image: http://research.geodan.nl/edugis/images/wmsoriginal.png
>
>
> The original image uses anti-aliasing with the alpha channel and the cached tile uses PNG8 without full alpha support (there is only a single full transparent color available). You need to disable palleted images and store the tiles as PNG24, or you need to upgrade PIL to a more recent developer version. See: http://mapproxy.org/docs/nightly/install.html#pil
>
After installing the 'new' PIL from source:

sudo aptitude install build-essential python-dev libjpeg-dev  zlib1g-dev 
libfreetype6-dev
sudo pip install 
https://bitbucket.org/olt/pil-2009-raclette/get/default.tar.gz

8 bit PNG caching with alpha channel works like a charm!

Thanks,

Anne