Hi Seth, nice work!
To your questions: - PNG24/32: lossless, so no quality-parameter, just compression efficiency (comparable to ZIP-Compression; size vs. needed time) [FORMATOPTION “ZLEVEL=n”] - PNG8: also lossless compression, but with color-depth-reduction (quantization), if you have data with more than 256 colors – this can/will be lossy; also holds transparency-information (look-up-table for defined colors can have rgba-values) - JPEG: IMHO the optimum for base-layers because of it’s small size and good performance (at least, if the base layer is not optimized with reduced color – png8); optimum for aerial images and “noisy” data; quality can be controlled as show downwards… - GeoTIFF: good solution, if you’d like to use the wms as “download-service” – images then hold complete GeoTIFF-Header (was buggy with older mapserver/GDAL-versions, but seems OK for now) Transparency can be controlled in different manners (in mapfile or in original data), at least these, please correct me: Mapfile: - LAYER-MASK (polygon-layer, outer area is transparent) - LAYER-OFFSITE (mapfile-NoData-value) Data-side: - NoData-value (e.g. GTIFF-Header) - Alpha/Transparency (e.g. GTIFF – per Pixel) - Mask-layer inside data (separate GDAL-special pixel-mask-layer inside GTIFF for full transparency; useful in combination with GTIFF inside JPEG-compression, because JPEG can’t hold alpha-channel and NoData doesn’t work calculable caused by lossy compression) If compiling GDAL and mapserver by your own, then using libjpeg-turbo instead of libjpeg brings some extra pieces of performance, specially when dealing with large amounts of image-data. You can define/modify default-formats and add special GDAL compression-options with ‘ FORMATOPTION “KEY=VALUE” ’, do not forget to add format to formatlist: http://pastebin.com/1YztvEcw Ben Luftbild und Geoinformationssysteme Kronprinzenstraße 6 45128 Essen Fon: +49 201 2069-232 Fax: +49 201 2069-500 schep...@rvr-online.de<mailto:schep...@rvr-online.de> Die Regionaldirektorin Kronprinzenstraße 35 45128 Essen Zentrale: +49 (0) 201 2069-0 Fax: +49 (0) 201 2069-500 www.metropoleruhr.de<http://www.metropoleruhr.de> Postfach 10 32 64 45032 Essen Steuernummer: RVR 112/5797/0116 USt.-ldNr.: DE 173867500
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