[mapserver-users] anti-aliasing (was differing image size with different mapserver versions)

[Richard Greenwood]

I do automatically switch to JPEG when there's imagery or similar content
and could use JPEG more except where I need transparency, like when
overlaying a tiled background layer in OpenLayers.
I messed with the Cairo driver a little but it seems less flexible than
AGG. I haven't been too happy with vector tiles. And yeah, I know GD isn't
an option. Thanks Steve.




On Tue, May 18, 2021 at 1:30 PM Steve Lime <sdlime at gmail.com> wrote:

> If you don't care about quality then JPEG is an option... ;-) I also
> wonder if there are ways to create true 8-bit output in other ways. No way
> GD comes back.
>
> On Tue, May 18, 2021 at 1:12 PM Richard Greenwood <
> richard.greenwood at gmail.com> wrote:
>
>> Oops - typo there, reducing the colors from 256 to *125* reduced the
>> image size by about 15%.
>>
>> On Tue, May 18, 2021 at 12:11 PM Richard Greenwood <
>> richard.greenwood at gmail.com> wrote:
>>
>>> Bob - I think GD was quite unpopular with the developers. Thomas Bonfort
>>> was pretty adamant about removing it. I'm hoping that there may be options
>>> in AGG.
>>>
>>> Seth - FORMATOPTION "COMPRESSION=9" only reduced the size by about 3% in
>>> my lines and text test case.
>>>
>>> Even - the default AGG/PNG8 has QUANTIZE_FORCE=on
>>> and QUANTIZE_COLORS=256. I think I remember you saying somewhere that
>>> reducing the number of colors mostly just reduced the pallet size and
>>> that's pretty much what I see. e.g. reducing the pallet from 256 to 15
>>> colors reduces the image size by about 15% in my lines and text test.
>>>
>>> Thanks all for the suggestions.
>>> Rich
>>>
>>>
>>> On Tue, May 18, 2021 at 11:49 AM Even Rouault <
>>> even.rouault at spatialys.com> wrote:
>>>
>>>> Forcing paletted images using QUANTIZE_FORCE=on and decreasing the number of colors with QUANTIZE_COLORS can also help:
>>>>
>>>>  FORMATOPTION "QUANTIZE_FORCE=on"
>>>>  FORMATOPTION "QUANTIZE_COLORS=200"
>>>>
>>>> Le 18/05/2021 à 19:30, Seth G a écrit :
>>>>
>>>> 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.
>>>>
>>>> --
>>>> web:http://geographika.co.uk
>>>> 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 <mapserver-users-bounces at lists.osgeo.org>
>>>> <mapserver-users-bounces at lists.osgeo.org> on behalf of Richard
>>>> Greenwood <richard.greenwood at gmail.com> <richard.greenwood at gmail.com>
>>>> *Date: *Tuesday, May 18, 2021 at 11:50 AM
>>>> *To: *"mapserver-users at lists.osgeo.org"
>>>> <mapserver-users at lists.osgeo.org> <mapserver-users at lists.osgeo.org>
>>>> <mapserver-users at lists.osgeo.org>
>>>> *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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>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>> -- http://www.spatialys.com
>>>> My software is free, but my time generally not.
>>>>
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>>>>
>>>
>>>
>>> --
>>> Richard W. Greenwood, PLS
>>> www.greenwoodmap.com
>>>
>>
>>
>> --
>> Richard W. Greenwood, PLS
>> www.greenwoodmap.com
>> _______________________________________________
>> mapserver-users mailing list
>> mapserver-users at lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/mapserver-users
>>
>

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