Re: [Cbor] typed arrays for complex numbers
Josef 'Jeff' Sipek <jeffpc@josefsipek.net> Thu, 18 July 2019 13:51 UTC
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Date: Thu, 18 Jul 2019 09:51:18 -0400
From: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
To: Gregory Allen <gallen@arlut.utexas.edu>
Cc: Carsten Bormann <cabo@tzi.org>, cbor@ietf.org
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Subject: Re: [Cbor] typed arrays for complex numbers
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On Mon, Jul 15, 2019 at 09:55:21 -0500, Gregory Allen wrote: > Perhaps “complex” deserves a special tag because it’s so common, My instinct is telling me that you are correct. If someone ever comes up with a more generic way to store vectors in arbitrary n-dimensional spaces, they can always say that complex numbers should use this other tag. > but it’s easy to see how a tag for each type of compound data doesn’t > scale well. > > Following Jeff’s line of reasoning could lead to something like structured > data types in NumPy > [https://docs.scipy.org/doc/numpy/user/basics.rec.html]. HDF5 supports > similar constructs. > > The idea is that one describes the type, and then an array can contain > elements of the user-defined type. This can be used to describe blobs > containing homogeneous arrays of arbitrary structures. > > For example (from NumPy): > > cymk_type = [(‘c’, np.uint8), (‘y’, np.uint8), (‘m’, np.uint8), (‘k’, np.uint8)] # list of (name, type) pairs > x = np.zeros([640, 480], dtype=cymk_type) > > I didn’t propose this before because it’s obviously much greater in scope > than adding a “complex” tag. It’s not even clear to me what approach I > would want to take to add this to CBOR. Interesting. I'd definitely want to leave this to someone who knows more about this / actually cares about this :) (That may be you, for all I know!) Jeff. > > Thanks, > -Greg > > > On Jul 12, 2019, at 9:17 AM, Josef 'Jeff' Sipek <jeffpc@josefsipek.net> wrote: > > > > On Fri, Jul 12, 2019 at 02:23:23 +0200, Carsten Bormann wrote: > >> On Jul 12, 2019, at 01:24, Gregory Allen <gallen@arlut.utexas.edu> wrote: > >>> > >>> I could imaging a “complex” tag, that’s a modifier for a dataType, so that one could do: > >>> > >>> multi-dim([dim, complex(ta-float32le(bstr)) ]) > >>> > >>> However, that doesn’t scale well to having several different compound types such as those mentioned above. > >> > >> Well, it requires a new tag for each of these compound types, but if these are indeed different types, then tags are cheap (as long as they don’t have to come out of the 1+1 space :-). > >> > >> So if this helps, we could indeed define tags (for complex, quaternion, > >> octonions, sedenions, RGB, RGBA) that extract groups of 2, 4, 8, 16, 3, 4 > >> elements out of an array (tagged or classical CBOR). > >> (Well, RGB is a bit weird, because there are so many color spaces. Maybe > >> just have tags for three- and four-dimensional color spaces.) > > > > I'm far from a color expert, but as far as I know even for RGB color spaces > > the values aren't always stored in one order. At the very least there are > > RGBA and ARGB. > > > > Currently my best idea amounts to: > > > > color(["RGB", [R1, G1, B1, R2, ...]) > > color(["RGBA", [R1, G1, B1, A1, R2, ...]) > > color(["CMYK", [C1, M1, Y1, K1, C2, ...]) > > > > I don't know if using a text string to identify the color component names > > and order is an anti-pattern in CBOR but it is similar to the currency > > related tags discussed some months ago. > > > > This could even be extended to support planar formats (where the values for > > each component are clumped together to allow better compression) and chroma > > subsampling (where there aren't the same number of samples for each > > component). With either: > > > > color(["RGB", [R1, R2, ...], [G1, G2, ...], [B1, B2, ...]) > > color(["YUV420", [Y1, Y2, ...], [U1, U2, ...], [V1, V2, ...]) > > > > or: > > > > color(["RGB", [R1, R2, ..., G1, G2, ..., B1, B2, ...]) > > color(["YUV420", [Y1, Y2, ..., U1, U2, ..., V1, V2, ...]) > > > > I suppose the second would need to identify the number or ratio of values > > for each component to support chroma subsampling, so the first would > > probably be better. > > > > Going down the rabbit hole of storing color data, there are also CCDs which > > red/blue pixels. > > > > > > Anyway, beware I know just enough about this to be dangerous :) I'd > > probably stay away from defining tags for colors until an actual expert > > comes along. > > > > Jeff. > > > >> Alternatively, supplying the group size separately maybe can do all of these at omce, but then cannot distinguish quaternions from RGBA or CMYK. > >> > >> Grüße, Carsten > >> > >> _______________________________________________ > >> CBOR mailing list > >> CBOR@ietf.org > >> https://www.ietf.org/mailman/listinfo/cbor > > > > -- > > My public PGP key can be found at https://www.josefsipek.net/pgp/ > -- You measure democracy by the freedom it gives its dissidents, not the freedom it gives its assimilated conformists. - Abbie Hoffman
- [Cbor] typed arrays for complex numbers Gregory Allen
- Re: [Cbor] typed arrays for complex numbers Carsten Bormann
- Re: [Cbor] typed arrays for complex numbers Josef 'Jeff' Sipek
- Re: [Cbor] typed arrays for complex numbers Gregory Allen
- Re: [Cbor] typed arrays for complex numbers Josef 'Jeff' Sipek