Re: filtering 16-bit samples
John Bowler <[email protected]>
| Newsgroups | gmane.comp.graphics.png.general |
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| Message-ID | <CAP7U39-wjo4GAo29BW2Pw3=sT3zRsr_iy=GRSdFZLtduuFzSUg@mail.gmail.com> |
On Sun, Jan 15, 2017 at 5:18 AM, Chris Lilley <[email protected]> wrote: > b) apply one of the existing filters (including none) to each field. The > Hi and Lo fields might well compress better if filtered differently. > That's likely to be true, the low 8 bits are likely to either contain a lot more noise or a lot more regularity depending on where they originated. > I haven't proposed it because I never took the time to run experiments > and see how it worked out in practice with various images. Has anyone > else wondered about this? > I've wondered about it but, like you, not tested it. Using separate filters is is one option, applying the filter 16 bits at a time (modulo 65535 rather than modulo 255) is another. The option which has been my favorite for investigation, however, is to compress the channels independently; they are already filtered independently, the idea would be to run up to four deflate streams in parallel. That said I'm more interested in compressing perceptual information losslessly than compressing a somewhat arbitrary digital encoding of that information losslessly. Apparently minor adjustments to PNG filtering, compression, or uncompressed data format are really creation of a new file format. The issue of higher dynamic range and more precise data not compressing as well is, I think, best addressed by looking at the broader issue of what the purpose of such data is and how it is best represented. I think it will be a few years before such data is in widespread use and it won't be possible to standardize anything until then. (Look at how fast the SLog stuff is changing.) -- John Bowler <[email protected]> +1 (541) 450-9885 PO BOX 3151 KERBY OR 97531-3151 USA ------------------------------------------------------------------------------ Developer Access Program for Intel Xeon Phi Processors Access to Intel Xeon Phi processor-based developer platforms. With one year of Intel Parallel Studio XE. Training and support from Colfax. Order your platform today. http://sdm.link/xeonphi _______________________________________________ png-mng-misc mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/png-mng-misc