[mapserver-dev] Paletted PNG and Quantization
cnieman at dmsolutions.ca
Fri Apr 13 11:22:22 EDT 2012
Just wanted to make sure that I'm doing this right before filing a bug:
With MapServer 6.0.2 and master, I wanted to have an 8-bit PNG with the
colours defined by a palette. In previous versions of MapServer, all I
had to do was put
in the OUTPUTFORMAT. When I did this in MapServer >= 6, I got a very
ugly output (looked like there was hardly any anti-aliasing happening).
Looking in mapimageio.c around line 422, I discovered that I needed to
also have FORMATOPTION "QUANTIZE_COLORS=<a number greater than 0>" in
the OUTPUTFORMAT or no quantization would happen to add the required
colours for anti-aliasing.
The documentation for the AGG/PNG driver explicitely says that
"PALETTE_FORCE=on" is used to reduce image depth with a predefined
palette. This option is incompatible with the previous quantization
options. But this would seem to no longer be true.
Is this a documentation error, or a problem in the mapimageio.c code?
DM Solutions Group, Inc.
Email: cnieman at dmsolutions.ca
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