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2007.04.06 18:41 "Re: Floating point RGBA", by Chris Cox
LZW will expand floating point data, as it frequently does with 16 bit data. ZIP does a decent job with straight floating point values. But to get good compression, you need a predictor that knows about the floating point format. (and I'm still researching better ones) Chris On 4/5/07 1:04 PM, "Toby Thain" <toby@smartgames.ca> wrote: > > On 5-Apr-07, at 4:58 PM, Craig Bruce wrote: > >> "Joris" <joris.at.lebbeke@skynet.be> wrote: >> >>> That seems like a very strange combination. If I remember correctly, >>> packbits is a byte-based RLE scheme. Applied to floating point data, >>> compression ought to be very inefficient. >> >> It may be a sensible option if the image has significant regions of >> solid black. The IEEE floating-point representation of 0.0 is: 0x00, >> 0x00, 0x00, 0x00 (in either endian). > > Dictionary compressors are much more likely to win, overall. RLE does > seem an odd choice, regardless of the actual data characteristics. > > --Toby > >> >> --------------------------+---------------------- >> +-------------------------- >> Dr. Craig S. Bruce | Ph 819-771-8303 x205 | >> CubeWerx Inc. >> Senior Software Developer | Fax 819-771-8388 | Gatineau, >> Québec, Canada >> csbruce@cubewerx.com | http://csbruce.com/ | http:// >> www.cubewerx.com/ >> --------------------------+---------------------- >> +-------------------------- >> "Hard work may not kill you, but why take chances?" >> _______________________________________________ >> Tiff mailing list: Tiff@lists.maptools.org >> http://lists.maptools.org/mailman/listinfo/tiff >> http://www.remotesensing.org/libtiff/ > > > _______________________________________________ > Tiff mailing list: Tiff@lists.maptools.org > http://lists.maptools.org/mailman/listinfo/tiff > http://www.remotesensing.org/libtiff/