On 10/23/2012 11:24 PM, Richard Greenwood wrote:
On Tue, Oct 23, 2012 at 7:30 PM, Stephen Woodbridge
<[email protected]> wrote:
On 10/23/2012 4:31 PM, Richard Greenwood wrote:
All -
I've have always used 8 bit GIFs because they are generally the
smallest. I serve a rural area with flaky internet and I do a good bit
with mobile, so size is more important to me than pixel-perfect.
Since MapServer 6.0 I have found 8 bit output (GIF or PNG) to be much
more buggy than 24 bit output. Bugs that I have been able to isolate
and report have been fixed very quickly by the devs, but I'm
struggling with a couple now that are sporadic and that I can not
shrink down to a reproducible bug report. I see the same issues in
Windows and Linux. I'm running 6.0.3 on both. So:
1. What image format are people generally using? Am I stuck in the
past with 8 bit images? Should I just go with 24 bit and not worry
that my images are several times larger?
2. My general sense is that the root of the issues I'm seeing are in
the shift from GD to AGG. Are PC256 PNGs generated by GD or AGG?
3. Any general advise for 8 bit output? For GIF is use the default (I
don't define an OUTPUTFORMAT block) for PNG I do define an
OUTPUTFORMAT block and use IMAGEMODE PC256.
The two issues that I'm struggling with right now are that my label
colors change as I pan and zoom, and that the HATCH fill pattern
extends outside of its polygons. In both cases switching from an 8 bit
output to a 24 bit output resolves the issue.
Thanks,
Rich
Rich,
I use this:
OUTPUTFORMAT
NAME "agg_qn"
DRIVER "AGG/PNG"
EXTENSION "png"
MIMETYPE "image/png"
IMAGEMODE RGB
FORMATOPTION "INTERLACE=false"
FORMATOPTION "QUANTIZE_NEW=ON"
FORMATOPTION "QUANTIZE_FORCE=ON"
FORMATOPTION "QUANTIZE_DITHER=OFF"
FORMATOPTION "QUANTIZE_COLORS=256"
#TRANSPARENT ON
#FORMATOPTION "TRANSPARENT=ON"
END
It gives me 8-bit png and I have no problem with it. Here is an example
using mapserver and mapcache
http://imaptools.com:8080/demo/tiger-tiles.html
And here is an example using just mapserver and draw on demand:
http://imaptools.com:8080/demo/tiger2011.html
I think both of these are using:
MapServer version 6.0.2 OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG SUPPORTS=PROJ
SUPPORTS=AGG SUPPORTS=FREETYPE SUPPORTS=ICONV SUPPORTS=FRIBIDI
SUPPORTS=WMS_SERVER SUPPORTS=WMS_CLIENT SUPPORTS=WFS_SERVER SUPPORTS=GEOS
INPUT=POSTGIS INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE
Hope this helps,
-Steve W
Thanks Steve. That's an improvement. The image is still much larger
than the default GIF, or PNG with IMAGEMODE PC256, but it does
eliminate at least one of my sporadic bugs.
I've attached two PNGs:
1. rgb-good.png is 67K and uses your suggested settings above.
2. pc256-bad.png is 34K and uses your settings above except changed to
IMAGEMODE PC256. You can see that the HATCH fill is completely
haywire.
In both cases the output PNG is 8 bit.
As always, I appreciate your insight.
Rich
Ahh, just got this. I'm not sure I have anything useful to say other
than: If it hurts, don't do that! :) Seriously, if you can live with a
jpeg, you might get the results you want in a smaller size, but I have
not tried it. That said, this does look like a bug, so maybe Thomas has
something to add.
-Steve W
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