On Tue, Apr 19, 2011 at 10:51 AM, thomas bonfort <[email protected]> wrote: > ok, I see where the issue is arising from: in 5.x you were using gd's > quantization algorithm, which to put it frankly, sucked badly (i.e. > note the duplicate entries in the color table which are a waste of > quality). > the current quantization algorithm is much higher quality, and thus > produces heavier images. If you want to return to something like GD, > try lowering the number of colors , e.g. QUANTIZE_COLORS=64 . Although > I'm not sure if by doing that the zlib compression will be able to > squeeze the final size down. As before, please post back your findings > if you try!
With quantize_colors 64 the size is reduced to 101kb, with 32 colors the size is 87kb and the quality i still good. I think this should be mentioned in migration.txt! Also, the documentation for 5.6 says http://mapserver.org/mapfile/outputformat.html: “QUANTIZE_COLORS=256” used to specify the number of colors to be used when applying quantization. Maximum value is 256. Specifying anything between 17 and 255 is probably a waste of quality as each pixel is still encoded with a full byte. Specifying a value under 16 will produce tiny images, but severly degraded. I think it will be hard to specify good values for quantize_colors as this is really dependent of the scale used (thinking WMS). An enhancement for Mapserver 6.1 would be some sort of auto tuning? Thanks for the support! /Erik _______________________________________________ mapserver-users mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/mapserver-users
