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VICAR Data Type Labels
As mentioned above, VICAR uses system label items to keep track of the machine
type the file (both image and binary label) was written on. These label
items are summarized below. Note that the label items are identical to the
keywords in Section , New Optional Keywords.
- HOST, string: The type of computer used to generate the image.
It is used only for documentation; the RTL uses the INTFMT and REALFMT label
items to determine the representation of the pixels in the file. Nevertheless,
it should be kept consistent with INTFMT and REALFMT.
Table lists the currently valid host labels and the machine
types they represent. New values for HOST will appear every time the RTL is
ported to a new machine, so the table is not necessarily a complete list.
Programs should not be surprised by values other than the ones listed below
appearing in the label.
- INTFMT, string: The format used to represent integers in the file.
INTFMT, REALFMT, and HOST should all match, so if you change one please
change all three.
The valid values of INTFMT may change as the RTL is ported to new machines.
However, the currently valid values are listed in Table .
- REALFMT, string: The format used to represent floating point
numbers in the file. INTFMT, REALFMT, and HOST should all match, so if you
change one please change all three.
The valid values of REALFMT may change as the RTL is ported to new machines.
However, the currently valid values are listed in Table .
- BHOST, string: The type of computer used to generate the binary
label. It is used only for documentation; the RTL uses the BINTFMT and
BREALFMT label items to determine the representation of the binary labels in
the file. Nevertheless, it should be kept consistent with BINTFMT and BREALFMT.
The valid values of BHOST are exactly the same as for the HOST label item above.
- BINTFMT, string: The format used to represent integers in the
binary label. BINTFMT, BREALFMT, and BHOST should all match, so if you change
one please change all three.
The valid values of BINTFMT are exactly the same as for the INTFMT label
item above.
- BREALFMT, string: The format used to represent floating point
numbers in the binary label. BINTFMT, BREALFMT, and BHOST should all match,
so if you change one please change all three.
The valid values of BREALFMT are exactly the same as for the REALFMT label
item above.
- BLTYPE, string: The type of the binary label. This is not type
in the sense of data type, but is a string identifying the kind of binary label
in the file. The RTL does not do any interpretation or checking of BLTYPE. It
is intended mainly for documentation, so people looking at the image will know
what kind of binary label is present. It may also be used by application
programs to make sure they can process the given type of binary label, or to
make sure it is processed correctly.
The valid values of BLTYPE are maintained in a name registry, so that all
possible kinds of binary labels can be documented in one place. Only names
that are registered should be used in BLTYPE. See Section ,
Binary Label Type, for more details.
In addition, one label item is used to specify the data type. It is not
new, but is listed here for completeness. It is unfortunate that the name
FORMAT is used for the data type, rather than for the host representation
(which would better be called format), but the names cannot be changed
for historical reasons.
- FORMAT, string: The data type of the pixels in the file. The valid
values are unlikely to change, unlike the host format labels. They are:
- BYTE
- : Single byte, unsigned integer pixel type.
- HALF
- : Signed short integer pixel type (often 2 bytes).
- FULL
- : Standard size signed integer pixel type (often 4 bytes).
- REAL
- : Single precision floating-point pixel type.
- DOUB
- : Double precision floating-point pixel type.
- COMP
- : Two single precision floating-point numbers representing a complex
pixel type, in the order (real, imaginary).