[mapserver-users] Mapserver rendering with 24 bit colour

[David Nugent]

On 06/05/2009, at 1:52 PM, David Nugent wrote:

> Once I completed upgrading to mapserver 5.4, I decided I'd give the  
> new AGG renderer a try.
> ~
> However, as a by-product of changing renderer, the metatiles  
> produced by mapserver differ slightly in colour. Some agree exactly  
> to the RBG colours I am providing, others are rendered with slight  
> variations, and when viewed on the web it becomes fairly obvious  
> where the meta tile borders are.



This is to follow up on my own question to which I received no  
response either on the list or otherwise in case anyone else runs into  
the same or a similar problem.

I finally found the problem in that the php mapscript had a bug, and  
that "AGG_Q" (AGG with quantize enabled) was being selected regardless  
that I was trying to tell it to do it differently. Once I correctly  
set it to AGG without quantize, the colour variation between tiles  
disappeared and all is well.

One interesting aspect of this is that the average file size did not  
increase significantly when dropping quantize although in general the  
tiles rendered using AGG are around 40-50% larger than PNG8.

Regards,
--
David Nugent (davidn at datalinktech.com.au)
Software Engineer
datalink technologies pty ltd
Mobile GPS/GPRS business process solutions
http://www.datalinktech.com.au/



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