[gdal-dev] Interpolation when using the WMS format

[Jukka Rahkonen]

Peter Hopfgartner <peter.hopfgartner <at> r3-gis.com> writes:


> I finally took the time to have a better look at this.
> 
> The attached patch is only for our special case, where data arrives in 8 
> bit bands  and is certainly far from being decent (I've written my last 
> C++ code approx. 15 years ago). Anyway, the image quality seems indeed 
> to improve sensibly.
> 
> I used the current SVN version as a base for the development.
> 
> Applying the patch I get from
> 
>
https://dl.dropboxusercontent.com/u/4935329/resampling_tests
/basemap.2000x2000-quasiorig.jpg

> to this
> 
>
https://dl.dropboxusercontent.com/u/4935329/resampling_tests
/basemap.2000x2000.bilinear.jpg



Hi Peter,

The improvement in quality is big, from almost unusable into rather good.

One more thing came into my mind because you said you are going to use this
for cascading tiles with Mapserver. From the Mapcache documentation
http://mapserver.org/mapcache/config.html I understood that this product of
Mapserver family can also do bilinear resampling:

<full_wms>assemble</full_wms>
<!-- resample mode
filter applied when resampling tiles for full wms requests.
can be either:
- nearest : fastest, poor quality
- bilinear: slower, higher qulity
-->
<resample_mode>bilinear</resample_mode>

It might be interesting for you to compare the code, speed and quality with
your solution.

-Jukka Rahkonen-