Annotation of /trunk/src/compiler/fields/dnorm-format.txt

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1 :	glk	107	The ASCII lines in the header end with '\n'.
2 :
3 :			First line should be the magic:
4 :			NRRD0004
5 :
6 :			Rest of header will be a sequence of plain text lines, terminated by
7 :			an empty line ('\n' alone). Some header lines give per-array
8 :	jhr	112	information, some give per-axis information.
9 :	glk	107
10 :	jhr	112	Note that the distinction between scalar and non-scalar images is
11 :			given by the per-axis "kinds" field, so that is where further
12 :			information is given about the constraints associated iwth non-scalar
13 :			image data.
14 :	glk	107
15 :			============================================================
16 :			The basic fields that should be there are:
17 :
18 :			----------------
19 :			type: <string>
20 :
21 :			Gives the type of the scalar values in the array. Current values are:
22 :			signed char
23 :			unsigned char
24 :			short
25 :			unsigned short
26 :			int
27 :			unsigned int
28 :			long long int
29 :			unsigned long long int
30 :			float
31 :			double
32 :
33 :			----------------
34 :			dimension: <int>
35 :
36 :			Gives the dimension of the array. Must be greater than 0. Current
37 :			code has a #define that limits the value to <= 16. The per-axis fields
38 :			will have this many pieces of information.
39 :
40 :			----------------
41 :			encoding: <string>
42 :
43 :			How scalar values are encoded on disk. Currently, should only see
44 :			"encoding: raw".
45 :
46 :			----------------
47 :			endian: <string>
48 :
49 :			Endian-ness of raw values saved on disk. Possibilities are:
50 :			little
51 :			big
52 :
53 :			----------------
54 :			space dimension: <int>
55 :
56 :			Gives the dimension of the world-space in which the array or oriented
57 :			(For now we're not allowing the named spaces that are given with the
58 :			"space: " field). The points and vectors given by "space origin"
59 :			and "space directions" will have this many coefficients, so this
60 :			field has to precede "space origin" and "space directions".
61 :
62 :			----------------
63 :			space origin: (<float1>,<float2>,...,<floatN>)
64 :
65 :			Gives the location of the center of the first sample (with index
66 :			space coordinates (0,0,0,...,0). The number of coefficients
67 :			separated by commas and bounded by parens (with optional whitespace
68 :			throughout) is given by the "space dimension" field. Each coefficient
69 :			is a floating point value (of the sort produced by printf("%g", val))
70 :
71 :			============================================================
72 :			The per-axis fields that should be there are as follows. The ordering
73 :			of these fields is always *fast* to *slow*, and the number of pieces
74 :			of information is always equal to the image dimension.
75 :
76 :			----------------
77 :			sizes: <int1> <int2> ... <intD>
78 :
79 :			The number of samples along each axis. Each integer value must be >= 0.
80 :
81 :			----------------
82 :			kinds: <string1> <string2> ... <stringD>
83 :
84 :			The kind of information represented by the samples along each axis. The
85 :			possible values are:
86 :
87 :			2-vector
88 :			3-vector
89 :			4-vector
90 :			2D-symmetric-matrix
91 :			2D-matrix
92 :			3D-symmetric-matrix
93 :			3D-matrix
94 :			space
95 :
96 :			The "space" kind is for a typical axis of the image, with samples that
97 :			subtend some region of the spatial domain of the image. All the other
98 :			kinds are the sequence of scalar values that compose a non-scalar
99 :	jhr	112	image value (vectors and tensors).
100 :	glk	107
101 :	jhr	112	We currently allow there to be *at* *most* *one* axis with a
102 :			non-"space" kind. We can have non-scalar image values, but we don't
103 :			have cartesian products of non-scalar image values. The non-"space"
104 :			kind can be anywhere in the axis ordering. If all the axis kinds are
105 :			"space", then then image data is for scalars, else it is for
106 :			non-scalar data.
107 :
108 :			In scalar data, the image "dimension" must equal the "space dimension".
109 :			In non-scalar data, the image "dimension" must equal *one* plus
110 :			the "space dimension". That is, the spatial axes have to form a
111 :			basis, not necessarily orthonormal, for world space (the vectors
112 :			are defined by the "space directions" field, below). Thus, a
113 :			3-D scalar image can't reside in a 2-D or 4-D world space, nor can
114 :			a 3-D vector image reside in a 3-D or 5-D world space.
115 :
116 :			We are currently not allowing the "measurement frame" field that
117 :			identifies the coordinate system in which these are measured relative
118 :			to the image orientation, so nothing should be assumed about the space
119 :			in which these coefficients are measured. The order of coefficients
120 :			for these non-scalar kinds is:
121 :
122 :	glk	107	2D-symmetric-matrix: Mxx Mxy Myy
123 :			2D-matrix: Mxx Mxy Myx Myy
124 :			3D-symmetric-matrix: Mxx Mxy Mxz Myy Myz Mzz
125 :			3D-matrix: Mxx Mxy Mxz Myx Myy Myz Mzx Mzy Mzz
126 :
127 :			----------------
128 :			space directions: (<x1>,<x2>,...,<xN>) (<x1>,<x2>,...,<xN>) ...
129 :			(and at most one of these vectors is actually "none")
130 :
131 :			These give the "direction" in world-space between successive samples
132 :			along each axis: the columns of the index-to-world transform matrix.
133 :			There is one per image axis, even for the axis of coefficients of
134 :			non-scalar image values. Because such an axis really has no spatial
135 :			extent, for this and only this axis, the space direction vector is
136 :			instead the string "none".
137 :
138 :			============================================================
139 :			Field ordering:
140 :
141 :			The fields should appear in this order:
142 :			type
143 :			dimension
144 :			space dimension
145 :			sizes
146 :			space directions
147 :			kinds
148 :			endian
149 :			encoding
150 :			space origin

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