background image
ISO/IEC 10918-1 : 1993(E)
x
i
y
i
C
TISO0780-93/d014
Nf
C
Nf-1
C
i
C
C
2
1
Samples
Line
Left
Top
Right
Bottom
a) Source image with multiple components
b) Characteristics of an image component
Figure A.1 Source image characteristics
FIGURE A-1 [D14] 8 cm = 313 %
A.2
Order of source image data encoding
The scan header (see B.2.3) specifies the order by which source image data units shall be encoded and placed within the
compressed image data. For a given scan, if the scan header parameter Ns
=
1, then data from only one source component
the component specified by parameter Cs
1
shall be present within the scan. This data is non-interleaved by definition.
If Ns > 1, then data from the Ns components Cs
1
through Cs
Ns
shall be present within the scan. This data shall always be
interleaved. The order of components in a scan shall be according to the order specified in the frame header.
The ordering of data units and the construction of minimum coded units (MCU) is defined as follows.
A.2.1
Minimum coded unit (MCU)
For non-interleaved data the MCU is one data unit. For interleaved data the MCU is the sequence of data units defined by
the sampling factors of the components in the scan.
A.2.2
Non-interleaved order (Ns
=
=
1)
When Ns
=
1 (where Ns is the number of components in a scan), the order of data units within a scan shall be left-to-right
and top-to-bottom, as shown in Figure A.2. This ordering applies whenever Ns
=
1, regardless of the values of
H
1
and V
1
.
TISO0790-93/d015
Left
Right
Top
Bottom
Figure A.2 Non-interleaved data ordering
FIGURE A.2 [D15] 3,5 cm = 136 %
CCITT Rec. T.81 (1992 E)
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