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A<span class="pl-c1">ctually, 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.</span>
<p><span class="pl-c1">Looking more closely at </span><span
class="pl-c1"><span class="pl-c1">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.<br>
</span></span></p>
<div class="moz-cite-prefix">Le 15/05/2021 à 19:07, Richard
Greenwood a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:CAHBySPZxeKXe-dVLB3tWLSyZm0UiKn7M8NBozVtq+Jg2ARViwA@mail.gmail.com">
<div dir="ltr">
<div dir="ltr">Even,
<div><br>
</div>
<div>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. </div>
<div><br>
</div>
<div>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 <a
href="https://www.mapserver.org/mapfile/outputformat.html"
moz-do-not-send="true">https://www.mapserver.org/mapfile/outputformat.html</a>
seems to suggest. <br>
</div>
<div><br>
</div>
<div>In any case, thanks again.</div>
<div>Rich</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sat, May 15, 2021 at 9:59
AM Even Rouault <<a
href="mailto:even.rouault@spatialys.com"
moz-do-not-send="true">even.rouault@spatialys.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote">
<div>
<p>Richard,</p>
<p>your 6.4 image is a interlaced PNG, whereas the 7.6 is
a non-interlaced one.</p>
<p>I see in the git history a relevant commit:</p>
<p>$ git show 9984b39cc8f74d60eb240728df660a172a118aad<br>
commit 9984b39cc8f74d60eb240728df660a172a118aad<br>
Author: Thomas Bonfort <a
href="mailto:thomas.bonfort@gmail.com" target="_blank"
moz-do-not-send="true"><thomas.bonfort@gmail.com></a><br>
Date: Sun Oct 5 15:59:44 2008 +0000<br>
<br>
rgba_png: don't interlace by default<br>
<br>
<br>
git-svn-id: <a
href="http://svn.osgeo.org/mapserver/trunk@7960"
target="_blank" moz-do-not-send="true">http://svn.osgeo.org/mapserver/trunk@7960</a>
7532c77e-422f-0410-93f4-f0b67bdd69e2<br>
<br>
diff --git a/maprgbapng.c b/maprgbapng.c<br>
index 105d8d61..c3615edd 100644<br>
--- a/maprgbapng.c<br>
+++ b/maprgbapng.c<br>
@@ -357,10 +357,13 @@ int
msSaveImageRGBAQuantized(gdImagePtr img, gdIOCtx *ctx,
outputFormatObj *form<br>
int bot_idx, top_idx;<br>
int remap[256];<br>
int reqcolors = atoi(msGetOutputFormatOption(
format, "QUANTIZE_COLORS", "256"));<br>
+ const char *interlace;<br>
ms_png_info info;<br>
info.width = gdImageSX(img);<br>
info.height = gdImageSY(img);<br>
- if( strcasecmp("ON", msGetOutputFormatOption(
format, "INTERLACE", "ON" )) == 0 )<br>
+ interlace = msGetOutputFormatOption( format,
"INTERLACE", "OFF" );<br>
+ if( strcasecmp("ON", interlace) == 0 ||
strcasecmp("YES", interlace) == 0<br>
+ || strcasecmp("1", interlace) == 0)<br>
info.interlaced=1;<br>
else<br>
info.interlaced=0;<br>
</p>
<p>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.<br>
</p>
<p>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.<br>
</p>
<p>Even<br>
</p>
<p><br>
</p>
<div>Le 15/05/2021 à 17:43, Richard Greenwood a écrit :<br>
</div>
<blockquote type="cite">
<div dir="ltr">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.
<div><br>
<div>OUTPUTFORMAT<br>
NAME "png-test"<br>
DRIVER "AGG/PNG" # GD driver is same (6.4 only)<br>
MIMETYPE "image/png; mode=8bit"<br>
IMAGEMODE PC256<br>
FORMATOPTION "QUANTIZE_FORCE=on"<br>
FORMATOPTION "QUANTIZE_COLORS=256"<br>
EXTENSION "png"<br>
# TRANSPARENT on or off makes little difference<br>
END</div>
<div><br>
</div>
<div><a
href="https://greenwoodmap.com/mapserv64.png"
target="_blank" moz-do-not-send="true">MapServer
6.4</a> is 90kB, <a
href="https://greenwoodmap.com/mapserv76.png"
target="_blank" moz-do-not-send="true">MapServer
7.6</a> 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?</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Rich</div>
</div>
<div><br>
</div>
-- <br>
<div dir="ltr">
<div dir="ltr">Richard W. Greenwood, PLS<br>
<a href="http://www.greenwoodmap.com"
target="_blank" moz-do-not-send="true">www.greenwoodmap.com</a></div>
</div>
</div>
<br>
<fieldset></fieldset>
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</pre>
</blockquote>
<pre cols="72">--
<a href="http://www.spatialys.com" target="_blank" moz-do-not-send="true">http://www.spatialys.com</a>
My software is free, but my time generally not.</pre>
</div>
</blockquote>
</div>
<br>
<div><br>
</div>
-- <br>
<div dir="ltr" class="gmail_signature">
<div dir="ltr">Richard W. Greenwood, PLS<br>
<a href="http://www.greenwoodmap.com" target="_blank"
moz-do-not-send="true">www.greenwoodmap.com</a></div>
</div>
</div>
</blockquote>
<pre class="moz-signature" cols="72">--
<a class="moz-txt-link-freetext" href="http://www.spatialys.com">http://www.spatialys.com</a>
My software is free, but my time generally not.</pre>
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