I've not used it but the following might help for the AGG/PNG driver:

FORMATOPTION "COMPRESSION=9"

https://mapserver.org/mapfile/outputformat.html

The default is 6. 

--
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twitter: @geographika


On Tue, May 18, 2021, at 7:16 PM, Basques, Bob (CI-StPaul) wrote:
> All,

>  

> I know the GD stuff has been a long running conversation in the MapServer 
> realm, but does this indicate that maybe discussing something on adding GD 
> back in might be prudent?  Or are there methods to get down to these previous 
> files sizes with the newer approaches?

>  

> I have the same concerns related to image size from the performance side, and 
> running on Mobile in our case.

>  

> Bobb

>  

>  

> *From: *mapserver-users <[email protected]> on behalf 
> of Richard Greenwood <[email protected]>
> *Date: *Tuesday, May 18, 2021 at 11:50 AM
> *To: *"[email protected]" <[email protected]>
> *Subject: *[mapserver-users] anti-aliasing (was differing image size with 
> different mapserver versions)

>  

> *Think Before You Click: *This email originated *outside *our organization.

>  

> Thanks to several helpful replies to my previous thread I know that the 
> increased image size between MapServer 6 with the GD driver and MapServer 7 
> with the AGG driver is due to differences in anti-aliasing (and lack of) in 
> the two drivers. (AGG features anti-aliasing and sub-pixel resolution 
> <https://en.wikipedia.org/wiki/Anti-Grain_Geometry>).

>  

> Gamma setting from 0-1 affects the size of a filled polygon layer by a factor 
> of almost 3x. But gamma has no effect on text, lines, and polygon outlines. 
> So images comprised of these types of features are approximately 2x larger 
> with the AGG/PNG8 driver than with the GD/GIF driver. 

>  

> Where else should I be looking to reduce my images sizes? I serve rural areas 
> with poor internet so in my case, smaller image sizes are more important than 
> higher quality images.

>  

> Thanks,

> Rich

>  

> --

> 

> Richard W. Greenwood, PLS
> www.greenwoodmap.com
> 

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