[mapserver-users] differing image size with different mapserver versions

[Even Rouault]

Actually, I just tried to open mapserv64.png with gimp, and export it as 
a non-interlaced or interlaced PNG. And the non-interlaced version is 60 
kB vs 96 kB for interlaced. So interlacing vs non-interlacing isn't the 
cause here.

Looking more closely at mapserv64.png  vs mapserv76.png , they are 
visually different. I suspect the rendering to be of higher quality in 
7.6 due to anti-aliasing and perhaps better quantization to 8-bit. You 
could perhaps try to turn off antialiasing in your CLASS.STYLE. This has 
been re-vived very recently for AGG line rendering. It is master only 
however.

Le 15/05/2021 à 19:07, Richard Greenwood a écrit :
> Even,
>
> Thank you. I had ignored the difference in the interlacing of the two 
> images because I didn't think it would have affected the size.
>
> The maprgbapng.c file no longer exists in MapServer 6.4 or 7.6. There 
> is an "if ( interlaced ..." code block in mapoutput.c that is the same 
> in 6.4 and 7.6. I tried forcing it ON and rebuilding 7.6 but the 
> output image still is not interlaced. Maybe that code is just a left 
> over. Or maybe AGG doesn't support interlacing as 
> https://www.mapserver.org/mapfile/outputformat.html 
> <https://www.mapserver.org/mapfile/outputformat.html> seems to suggest.
>
> In any case, thanks again.
> Rich
>
>
>
> On Sat, May 15, 2021 at 9:59 AM Even Rouault 
> <even.rouault at spatialys.com <mailto:even.rouault at spatialys.com>> wrote:
>
>     Richard,
>
>     your 6.4 image is a interlaced PNG, whereas the 7.6 is a
>     non-interlaced one.
>
>     I see in the git history a relevant commit:
>
>     $ git show 9984b39cc8f74d60eb240728df660a172a118aad
>     commit 9984b39cc8f74d60eb240728df660a172a118aad
>     Author: Thomas Bonfort <thomas.bonfort at gmail.com>
>     <mailto:thomas.bonfort at gmail.com>
>     Date:   Sun Oct 5 15:59:44 2008 +0000
>
>         rgba_png: don't interlace by default
>
>
>         git-svn-id: http://svn.osgeo.org/mapserver/trunk@7960
>     <http://svn.osgeo.org/mapserver/trunk@7960>
>     7532c77e-422f-0410-93f4-f0b67bdd69e2
>
>     diff --git a/maprgbapng.c b/maprgbapng.c
>     index 105d8d61..c3615edd 100644
>     --- a/maprgbapng.c
>     +++ b/maprgbapng.c
>     @@ -357,10 +357,13 @@ int msSaveImageRGBAQuantized(gdImagePtr img,
>     gdIOCtx *ctx, outputFormatObj *form
>          int bot_idx, top_idx;
>          int remap[256];
>          int reqcolors = atoi(msGetOutputFormatOption( format,
>     "QUANTIZE_COLORS", "256"));
>     +    const char *interlace;
>          ms_png_info info;
>          info.width = gdImageSX(img);
>          info.height = gdImageSY(img);
>     -    if( strcasecmp("ON", msGetOutputFormatOption( format,
>     "INTERLACE", "ON" )) == 0 )
>     +    interlace = msGetOutputFormatOption( format, "INTERLACE",
>     "OFF" );
>     +    if( strcasecmp("ON", interlace) == 0 || strcasecmp("YES",
>     interlace) == 0
>     +            || strcasecmp("1", interlace) == 0)
>              info.interlaced=1;
>          else
>              info.interlaced=0;
>
>     But this predates 6.4 release by several years, so this doesn't
>     explain why you see a different behavior, unless something in 6.4
>     still turned on interlacing on in that configuration.
>
>     From what I can see in the doc, the interlacing mode was removed
>     in the 7.0 release when GD went off, so I don't think you can do
>     much. I guess that could be re-added but would require some coding.
>
>     Even
>
>
>     Le 15/05/2021 à 17:43, Richard Greenwood a écrit :
>>     I get significantly different image sizes between MapServer 6.4
>>     and 7.6 with the same output format definition. I've tried many
>>     variations of the following.
>>
>>     OUTPUTFORMAT
>>       NAME "png-test"
>>       DRIVER "AGG/PNG"  # GD driver is same (6.4 only)
>>       MIMETYPE "image/png; mode=8bit"
>>       IMAGEMODE PC256
>>       FORMATOPTION "QUANTIZE_FORCE=on"
>>       FORMATOPTION "QUANTIZE_COLORS=256"
>>       EXTENSION "png"
>>       # TRANSPARENT on or off makes little difference
>>     END
>>
>>     MapServer 6.4 <https://greenwoodmap.com/mapserv64.png> is 90kB,
>>     MapServer 7.6 <https://greenwoodmap.com/mapserv76.png> is 320kB.
>>     Any suggestions as to how I can get my MapServer 7.6 image sizes
>>     down closer to what I'm getting in MapServer 6.4?
>>
>>     Thanks,
>>     Rich
>>
>>     -- 
>>     Richard W. Greenwood, PLS
>>     www.greenwoodmap.com <http://www.greenwoodmap.com>
>>
>>     _______________________________________________
>>     mapserver-users mailing list
>>     mapserver-users at lists.osgeo.org  <mailto:mapserver-users at lists.osgeo.org>
>>     https://lists.osgeo.org/mailman/listinfo/mapserver-users  <https://lists.osgeo.org/mailman/listinfo/mapserver-users>
>
>     -- 
>     http://www.spatialys.com  <http://www.spatialys.com>
>     My software is free, but my time generally not.
>
>
>
> -- 
> Richard W. Greenwood, PLS
> www.greenwoodmap.com <http://www.greenwoodmap.com>

-- 
http://www.spatialys.com
My software is free, but my time generally not.

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