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How to mix RowInterleaveFactor with SubTileBlockSize?

Guest
Mar 21, 2017 Mar 21, 2017

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My image tile is laid out as follows:

p00 p01 p02 p03

p10 p11 p12 p13

p20 p21 p22 p23

p30 p31 p32 p33

When using a RowInterleaveFactor = 2, the order within the file becomes:

p00 p01 p02 p03 p20 p21 p22 p23 p10 p11 p12 p13 p30 p31 p32 p33

When using a SubTileBlockSize = (2, 2), the order within the file becomes:

p00 p01 p10 p11 p02 p03 p12 p13 p20 p21 p30 p31 p22 p23 p32 p33

(This is neat, if you want to use a 4-channel predictor for compressing Bayer-patterned data)

When combining both (why-ever), the order of their application matters:

Row-interleaving first temporarily results in:

p00 p01 p02 p03

p20 p21 p22 p23

p10 p11 p12 p13

p30 p31 p32 p33

Sub-tiling afterwards:

p00 p01 p20 p21 p02 p03 p22 p23 p10 p11 p30 p31 p12 p13 p32 p33

But sub-tiling first temporarily results in something like:

p00 p01 p10 p11

p02 p03 p12 p13

p20 p21 p30 p31

p22 p23 p32 p33

Row-interleaving afterwards:

p00 p01 p10 p11 p20 p21 p30 p31 p02 p03 p12 p13 p22 p23 p32 p33

(this feels plain wrong!)

Which result is expected? Don't get me wrong on this: I don't see a single reason to combine both methods, but a conforming reader has to cope with this case since it's not forbidden by the specification.

Bonus question: What happens if the dimensions given in RowInterleaveFactor or SubTileBlockSize (or their product, if combining is allowed) cannot equally divide the tiles' dimensions? This also should be forbidden IMHO.

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