Manages the information associated with JPEG2000
QCD and
QCC marker segments. Tile- and component-specific forms
are allowed (in fact, required for a complete code-stream
description).
The cluster name is "QCD", but you are recommended
to use the macro
QCD_params, in functions which take a cluster name like
kdu_params::access_cluster.
The following attributes are defined. For an explanation
of pattern strings, consult the comments appearing
with
kdu_params::parse_string.
-
Macro =
Qguard; Pattern = "I" — Number of guard bits to prevent
overflow in the magnitude bit-plane representation.
Typical values are 1 or 2. Default is 1.
-
Macro =
Qderived; Pattern = "B" — Quantization steps derived
from LL band parameters? If true, all quantization
step sizes will be related to the LL subband's step
sizes through appropriate powers of 2 and only the
LL band step size will be written in code-stream markers.
Otherwise, a separate step size will be recorded for
every subband. You cannot use this option with reversible
compression. Default is not derived.
-
Macro =
Qstep; Pattern = "F" — Base step size to be used in
deriving irreversible quantization step sizes for every
subband. The base step parameter should be in the range
0 to 2. Default is 1/256.
-
Macro =
Qabs_steps; Pattern = "F", [MULTI_RECORD] — Absolute quantization
step sizes for each subband, expressed as a fraction
of the nominal dynamic range for that subband. The
nominal range is equal to 2^B (B is the image sample
bit-depth) multiplied by the DC gain of each low-pass
subband analysis filter and the AC gain of each high-pass
subband analysis filter, involved in the construction
of the relevant subband. The bands are described one
by one, in the following sequence: LL_D, HL_D, LH_D,
..., HL_1, LH_1, HH_1. Here, D denotes the number of
DWT levels. A single step size must be supplied for
every subband (there is no extrapolation), except in
the event that
Qderived is set to true — then, only one parameter is
allowed, corresponding to the LL_D subband. For compressors,
the absolute step sizes are ignored if
Qstep has been used.
-
Macro =
Qabs_ranges; Pattern = "I", [MULTI_RECORD] — Number of range
bits used to code each subband during reversible compression.
Subbands appear in the sequence, LL_D, HL_D, LH_D,
..., HL_1, LH_1, HH_1, where D denotes the number of
DWT levels. The number of range bits for a reversibly
compressed subband, plus the number of guard bits (see
Qguard), is equal to 1 plus the number of magnitude bit-planes
which are used for coding its samples. For compressors,
most users will accept the default policy, which sets
the number of range bits to the smallest value which
is guaranteed to avoid overflow or underflow in the
bit-plane representation, assuming that the RCT (colour
transform) is used. If explicit values are supplied,
they must be given for each and every subband.
qcd_params {Java: Qcd_params}