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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hi Gary,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>It is a well known fact that JPG introduces compression
artifacts at hard image boundaries. I suspect this will happen with text
and labels. PNG32 (just PNG in MapGuide) is a lossless compression format
so there will be no artifacts introduced.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>PNG8 is also lossless if have less that 256 colors in the
image. If you have tens of thousands of colors, there could be loss of
detail. I haven’t tried this personally but rendering text and
other vector data on top of detailed raster imagery could result in loss of
detail. When we convert to PNG8, we use a palette optimized for the
image. However, the detailed raster imagery will probably get more of the
palette since it occupies more image pixels than the vector imagery.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If you are using raster base imagery, have you tried moving the base
imagery into a tiled base layer? The tiled base layer and “normal”
layers are returned in separate map requests. This would give you two
independent color spaces and may improve the readability of text and labels.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Thanks,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Trevor<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Gary Morin
[mailto:gary.morin@keynetix.com] <br>
<b>Sent:</b> Thursday, March 20, 2008 3:58 AM<br>
<b>To:</b> mapguide-users@lists.osgeo.org<br>
<b>Subject:</b> [mapguide-users] Render services image formats <o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>Hi<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>I’ve been
investigating the render services image formats in an attempt to improve
performance over the internet<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>My first
observation, it appears in MGOS 2 setting the image format in serverconfig.ini
does not affect the formats being served, it was only when I edited the
ajaxmappane.templ did I see a difference.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>I know the default
is PNG, but we can change it JPG and with MGOS2 PNG8.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>The problem is,
with PNG the map images look great, but the download size is enormous,
I’m using some raster maps and the downloads are in the region of 1.5mb.
on my internet connection it is taking in the region of 6 seconds to display
the map after a pan. <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>If I switch to JPG
the download is much faster, the downloaded images are around 250K, but the
quality is poor, some text and labels are now unreadable.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>I have also tried
the new PNG8 format, but its results were very similar to JPG, image quality is
poor.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>Many of my clients
are use to working with the old MG 6.5, even with raster files being served it
performance was great.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>Is there a way to
alter the compression ratio of a format or any plans to allow this to be done
in the future? <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>Thanks<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'>Gary<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt'><o:p> </o:p></span></p>
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