Hi Juan,
Many thanks for getting back" really appreciated:-)
I have reread the XISF-1.0 spec from:
https://pixinsight.com/doc/docs/XISF-1.0-spec/XISF-1.0-spec.htmlSection 9.2 is Monolithic XISF File, which is what I always thought the Preview XISF
created from pixinsight was (which is what I'm parsing).
In Figure 8 "Structure of a monolithic XISF File" , after the XISF Header and Unused Space,
is the "Attached XISF data block". Both the end of the Unused space and the XISF Header,
point this to be byte 4096. So I am after the XISF data block format, and 2 sections further
it seems to be discussed.
Section 9.4 "XISF Data Blocks File", the goes onto talk about "An XISF data blocks file
shall have the following structure" :the Signature (A sequence of eight contiguous bytes
whose values must form the set 'XISB0100'). It state that block files can be local or remote.
Section 10.1"Attached XISF Data Block" has:
> An attached XISF data block is an XISF data block stored in a monolithic XISF file.
>
>The position of an attached data block from the beginning of the monolithic XISF file
>where it is stored, as well as its length in bytes, must be completely and unambiguously
>defined by the XISF header of the XISF unit.
>
>Attached XISF data blocks shall not occur in a distributed XISF unit.
So Attached XISF data blocks are in monolith and not distributed. The XISF data block
hyperlink does back to section 10
In the XISF header, the Image is described as:
<Image
geometry="555:483:3"
sampleFormat="Float32"
bounds="0:1"
colorSpace="RGB"
location="attachment:4096:3216780"
>
So my file's location is attachment :-)
Section 10.3 has a bullet '"location="attachment:position:size"' and states "Defines an
attached XISF data block in a monolithic XISF file": which is what I have.
So, given that the monolith description states that I should have an attached XISF data
block (Figure 8), the description of the data block in 9.4 states that it should have the
XIFB0100 signature.
It looks like the spec on the website therefore has some ambiguity ;-)
Where else, apart from Section 10.1,should I get the format of XISF data block used in a monolith XISF file ?
Do I just assume that a data block is described from Figure 9, from the start of the block index, (as the data block in this diagram states 'Position and length defined by a block index element, so needs the preamble from a block index) ?
=>an
attached XISF block definition is Figure 9 (minus the XISB signature and 8 bytes reserved ??)
I hope my explanation above is useful, as a newbie reading the spec. I hope you can point
me to where I've slipped up ?
best regards
Colin Thomas