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

[Oliver Tonnhofer]

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


Regards,
Oliver

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