Interpolate image

[Daniel Morissette]

I think Guillaume is correct that AGG's main advantages are on the 
vector side and unless I'm mistaken you won't see much difference with 
rasters. Thomas or others who worked on AGG support can correct me if 
I'm wrong.

Back to Pål's question, if I understood correctly, you're looking for a 
way to do bilinear resampling. This has been supported since MapServer 
4.8, see RFC-4 for the details:
   http://mapserver.gis.umn.edu/development/rfc/ms-rfc-4

Note that bilinear resampling was not working for AGG output in 
5.0.0-rc2 and this was fixed in the 5.0.0 release (that's one of the two 
fixes that were made after RC2.) ... you'll have to wait for a new MS4W 
with the release version of MapServer 5.0.0 to test this with AGG, but 
you can already test it with GD with RC2. I heard that Jeff was working 
on a new MS4W release yesterday, so it should be available very soon.

Daniel


Guillaume Sueur wrote:
> I think AGG optimization only applies on vector data. Am I wrong ?
> 
> Guillaume
> 
> Pål Kristensen a écrit :
>> Hi!
>>
>> I have recently installed ms4w 2.2.6 beta which include MS 5.0 RC2. The
>> reason for this was to test the new AGG rendering engine when using
>> Mapserver as a WMS server, with only high resolution (RGB) rasters as the
>> data source. Most WMS servers around (both free and commercial) uses 
>> nearest
>> neighbor interpolation on the resulting image that is transfered to the
>> client. In situations where the source data is only hires rasters or 
>> imagery
>> (as in my case), the quality of the output would be much better if you 
>> could
>> apply an bilinear interpolation to the produced image (see the attached
>> images for an example). Because in most cases the pixels in the source 
>> data
>> and the pixels on the screen do not match up, even if I have produces
>> pyramids on the source data (using gdal gdaladdo with the average option
>> sett). The only WMS servers that has the ability to interpolate the
>> resulting image with bilinear interpolation (that I have discovered) 
>> is the
>> ESRI ArcIMS ArcMap image service and the ESRI ArcGIS Server.
>>
>> I kind of hoped that the new AGG rendering back-end would give an 
>> option to
>> set the interpolation method used in the output, but I see no difference
>> when using AGG instead of GD. (IMAGEMODE is 24bit (RGB) PNG in both 
>> cases).
>> Am I missing something here, or do not AGG increase the image quality 
>> if the
>> resulting image if the data source is only rasters? Does anyone have any
>> experience concerning this issue, and maybe could give me some advice?
>>
>> ArcGIS Server
>> http://www.nabble.com/file/p12754990/ArcGIS_Server.png
>>
>> Mapserver 5.0 rc2 with AGG rendering
>> http://www.nabble.com/file/p12754990/MapServer_5rc2_AGG.png
>> Regards,
>> Pål Kristensen
>> Norwegian Mapping and Cadastre Authority
> 
> 


-- 
Daniel Morissette
http://www.mapgears.com/