Archived posting to the Leica Users Group, 2015/07/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Yew, I know. I was just surprised at first that it could be a factor of two. Then I stopped being surprised after I thought about it for a few minutes. Herbert Kanner kanner at acm.org 650-326-8204 Question authority and the authorities will question you. > On Jul 14, 2015, at 7:28 PM, Richard Man <richard at richardmanphoto.com> > wrote: > > Lossless compression is not new or difficult, even Huffman did it in 1952 > as a term paper project :-) > > On Tue, Jul 14, 2015 at 6:55 PM, Herbert Kanner <kanner at acm.org> wrote: > >> I was surprised to see in the manual that there was lossless compression >> of the DNG. So I thought I'd try it out by taking two shots, one >> compressed >> and one uncompressed. When I looked at my DNG file, I was astounded to >> find >> a DNG of over 40 MB and a compressed one of about half that size. (I >> deleted the negatives before thinking of writing this, so I can't give you >> exact numbers. >> >> Well, I was at first astounded that lossless compression could be that >> effective. Then I thought about the details of an image. Except where >> there >> is really fine structure in the image, there will be areas where the data >> does not change. A simple number triple, one giving a value for, say the >> red pixel, the second giving a starting location in the file, and the the >> third the number of consecutively stored pixels having the same value, >> could easily result in a factor of two compression for lots of pictures. >> And what I just described is a very unsophisticated compression method. If >> anyone knows more about how this might have been done, I'd be very >> interested. >> >> kanner at acm.org >> 650-326-8204 >> >> Question authority and the authorities will question you. >> >> >> >> >> >> _______________________________________________ >> Leica Users Group. >> See http://leica-users.org/mailman/listinfo/lug for more information > > > > > -- > // richard <http://www.richardmanphoto.com> > // http://facebook.com/richardmanphoto > // https://instagram.com/richardmanphoto > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information