Hi Steve, and everyone else, Thanks for your responce!
Late last night I discovered what the issue was. It took me several days of reading other people's problems and solutins in this area. It turned up that it is not the Mapserver settings, but the PHP functions I use to save the immage on the HD. I am using PHP "imagepng" after cropping the original image to remove the "gutter". However the function always seems to saves the image using 24 bits for colour mapping even if a palette is used and the colours are less than 256. The solution was to use "imagetruecolortopalette" PHP function like this - imagetruecolortopalette($tile_image, false, 256) I have to do some more investigation, but the PNG file now is using 8 bits for colours and is dramaticaly amaller. Best regards, Nick -----Original Message----- From: Steve Lime [mailto:[email protected]] Sent: 07 July 2009 16:07 To: [email protected]; [email protected] Subject: Re: [mapserver-users] Mapserver 5.2.0 and 5.4.1,QUANTIZE_FORCEor PALETTE_FORCE do not produce8bit colour PNG file - onlyreduce the number of colours used. Hi Nikolai: I'm using the exact same output format and it works fine for me (PALETTE_FORCE, 5.4.1). With that format my output images are 1/4 the size of their RGB counterparts. Have you tried a version without any of the experimental PNG options enabled? Steve >>> "Nikolai Nikolov" <[email protected]> 07/07/09 6:48 AM >>> Hi everybody, I have tried unsuccessfully to reduce the size of my PNG image tiles, generated by the Mapserver using the QUANTIZE_FORCE or PALETTE_FORCE options. The resulting file is marginally smaller than the one not using those options. Using "IrfanView" I could get some information about the colours used and the number of bits used to code the colours. The repost shows a decrease of the number of colours used from over 1600 to either 241 (Mapserver defined) or 193 (using palette file containing 71 predefined colours). However, tool reports 24 bits used for colour mapping. If I put the PNG image through tools like "pngquant", "OptiPng" or "pngcrush", the resulting image is much smaller and "IrfanView" reports that only 8 bits are used for colour mapping! The relevant map file part is: IMAGETYPE AGG_PNG24 OUTPUTFORMAT NAME AGG_PNG24 DRIVER AGG/PNG MIMETYPE "image/png" IMAGEMODE RGB EXTENSION "png" FORMATOPTION "PALETTE_FORCE=TRUE" FORMATOPTION "PALETTE=/var/www/html/maps_gypsii/palette.txt" FORMATOPTION "INTERLACE=OFF" END The Mapserver, both 5.2.0 and 5.4.1, has been configured with --with-experimental-png or --enable-experimental-png (I have not noticed any difference in using either option). Please, advise what I am missing here. Many thanks, Nick _______________________________________________ mapserver-users mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/mapserver-users
