AXES = _LOGICAL (Read)
TRUE
if labelled and annotated axes are
to be drawn around the image. These display co-ordinates in the current
co-ordinate
Frame of the supplied NDF, and may be changed using application
WCSFRAME (see also
Parameter USEAXIS). The width of the margins left for the annotation may be controlled
using Parameter MARGIN. The appearance of the axes (colours, founts,
etc.) can be
controlled using the STYLE Parameter.
[
current value
]
BADCOL = LITERAL (Read)
The
colour with which to mark any bad (
i.e. missing) pixels in the display. There are a
number of options described below.
-
"MAX"
–- The maximum colour index used for the display of the image.
-
"MIN"
–- The minimum colour index used for the display of the image.
-
An integer –- The actual colour index. It is constrained between 0 and the maximum
colour index available on the device.
-
A named colour –- Uses the named colour from the palette, and if it is not present, the
nearest colour from the palette is selected.
-
An HTML colour code such as #ff002d
.
If the colour is to remain unaltered as the lookup table is manipulated choose an
integer between 0 and 15, or a named colour. The suggested default is the current
value. [
current value]
BORDER = _LOGICAL (Read)
TRUE
if a border is to be drawn
around the regions of the displayed image containing valid co-ordinates in the current
co-ordinate Frame of the NDF. For instance, if the NDF contains an Aitoff all-sky map,
then an elliptical border will be drawn if the current co-ordinate Frame is galactic
longitude and latitude. This is because pixels outside this ellipse have undefined
positions in galactic co-ordinates. If, instead, the current co-ordinate Frame had been
pixel co-ordinates, then a simple box would have been drawn containing the whole image.
This is because every pixel has a defined position in pixel co-ordinates. The
appearance of the border (colour, width, etc.) can be controlled using Parameter
BORSTYLE. [
current value]
BORSTYLE = GROUP (Read)
A group of attribute
settings describing the plotting style to use for the border (see Parameter
BORDER).
A comma-separated list of strings should be given in which each string is either an
attribute setting, or the name of a text file preceded by an up-arrow character
""
.
Such text files should contain further comma-separated lists which will be read and
interpreted in the same manner. Attribute settings are applied in the order in which
they occur within the list, with later settings overriding any earlier settings given
for the same attribute.
Each individual attribute setting should be of the form:
name=value
where name
is the name of a plotting attribute, and
value
is the value to assign to the attribute. Default values will be used for any
unspecified attributes. All attributes will be defaulted if a null value (!
)–-the
initial default–-is supplied. To apply changes of style to only the current invocation,
begin these attributes with a plus sign. A mixture of persistent and temporary style
changes is achieved by listing all the persistent attributes followed by a plus sign
then the list of temporary attributes.
See Section E for a description of the available attributes. Any unrecognised
attributes are ignored (no error is reported). [
current value]
CENTRE = LITERAL
(Read)
The co-ordinates of the data pixel to be placed at the centre of the image, in
the current co-ordinate Frame of the NDF (supplying a colon
":"
will display details of
the current co-ordinate Frame). The position should be supplied as a list of
formatted axis values separated by spaces or commas. See also Parameter USEAXIS.
A null (
!
) value causes the centre of the image to be used.
[!]
CLEAR =
_LOGICAL (Read)
TRUE
if the current picture is to be cleared before the image is
displayed. [
current value]
The NDF array component to be
displayed. It may be "Data"
, "Quality"
, "Variance"
, or "Error"
(where "Error"
is an
alternative to "Variance"
and causes the square root of the variance values to be
displayed). If "Quality"
is specified, then the quality values are treated as
numerical values (in the range 0 to 255). ["Data"]
DEVICE = DEVICE (Read)
The name of the graphics device used to display the image. The device must
have at least 24 colour indices or grey-scale intensities. [
current graphics
device]
FILL = _LOGICAL (Read)
If FILL is set to TRUE
, then the image
will be ‘stretched’ to fill the current picture in both directions. This can
be useful when displaying images with markedly different dimensions, such as
two-dimensional spectra. The dynamic default is TRUE
if the array being displayed
is one-dimensional, and FALSE
otherwise. []
HIGH = _DOUBLE (Read)
The
data value corresponding to the highest pen in the colour table. All larger
data values are set to the highest colour index when HIGH is greater than LOW,
otherwise all data values greater than HIGH are set to the lowest colour index. The
dynamic default is the maximum data value. There is an efficiency gain when both
LOW and HIGH are given on the command line, because the extreme values need
not be computed. (Scale mode)
IN = NDF (Read)
The input NDF structure
containing the data to be displayed.
KEY = _LOGICAL (Read)
TRUE
if a key to the
colour table is to be produced to the right of the display. This can take the
form of a colour ramp, a coloured histogram of pen indices, or graphs of RGB
intensities, all annotated with data value. The form and appearance of this key can be
controlled using Parameter KEYSTYLE, and its horizontal position can be controlled
using Parameter KEYPOS. If the key is required in a different location, set
KEY=NO and use application
LUTVIEW after displaying the image.
[TRUE]
KEYPOS(
2 ) = _REAL (Read)
The first element gives the gap between the right-hand
edge of the display and the left-hand edge of the key, as a fraction of the
width of the current picture. If a key is produced, then the right-hand margin
specified by Parameter MARGIN is ignored, and the value supplied for KEYPOS is used
instead.
The second element gives the vertical position of the key as a fractional value in the
range zero to one: zero puts the key as low as possible, one puts it as high as
possible. A negative value (no lower than -1
) causes the key to match the height of the
display image. This may mean any text, like a label, for the horizontal axis may not
appear, though if AXES is TRUE
there is usually room. [
current value]
KEYSTYLE =
GROUP (Read)
A group of attribute settings describing the plotting style to use for
the key (see Parameter KEY).
A comma-separated list of strings should be given in which each string is either an
attribute setting, or the name of a text file preceded by an up-arrow character
""
.
Such text files should contain further comma-separated lists which will be read and
interpreted in the same manner. Attribute settings are applied in the order in which
they occur within the list, with later settings overriding any earlier settings given
for the same attribute.
Each individual attribute setting should be of the form:
name=value
where name
is the name of a plotting attribute, and
value
is the value to assign to the attribute. Default values will be used for any
unspecified attributes. All attributes will be defaulted if a null value (!
)–-the
initial default–-is supplied. To apply changes of style to only the current invocation,
begin these attributes with a plus sign. A mixture of persistent and temporary style
changes is achieved by listing all the persistent attributes followed by a plus sign
then the list of temporary attributes.
See Section E for a description of the available attributes. Any unrecognised
attributes are ignored (no error is reported).
Axis 1 is always the data value axis. So for instance, to set the label for the
data-value axis, assign a value to "Label(1)"
in the supplied style.
To get a ramp key (the default), specify "form=ramp"
. To get a histogram key (a
coloured histogram of pen indices), specify "form=histogram"
. To get a graph key (three
curves of RGB intensities), specify "form=graph"
. If a histogram key is produced, the
population axis can be either logarithmic or linear. To get a logarithmic population
axis, specify "logpop=1"
. To get a linear population axis, specify "logpop=0"
(the
default). To annotate the long axis with pen numbers instead of pixel value, specify
"pennums=1"
(the default, "pennums=0"
, shows pixel values). [
current value]
LOW =
_DOUBLE (Read)
The data value corresponding to the lowest pen in the colour
table. All smaller data values are set to the lowest colour index when LOW
is less than HIGH, otherwise all data values smaller than LOW are set to the
highest colour index. The dynamic default is the minimum data value. There is an
efficiency gain when both LOW and HIGH are given on the command line, because
the extreme values need not be computed. (Scale mode)
LUT = NDF (Read)
Name of the NDF containing a colour lookup table in its Data array; the lookup
table is written to the graphics device’s colour table. The purpose of this
parameter is to provide a means of controlling the appearance of the image on
certain devices, such as colour printers, that do not have a dynamic colour
table (
i.e. the colour table is reset when the device is opened). If used with
dynamic devices (such as X-windows), the new colour table remains after this
application has completed. A null value (
!
) causes the existing colour table to be
used.
The LUT must be two-dimensional, the dimension of the first axis being 3, and the
second being arbitrary. The method used to compress or expand the colour table if the
second dimension is different from the number of unreserved colour indices
is controlled by Parameter NN. Also the LUT’s values must lie in the range
0.0–1.0. [!]
MARGIN( 4 ) = _REAL (Read)
The widths of the margins to leave
around the image for axis annotations, given as fractions of the corresponding
dimension of the current picture. The actual margins used may be increased to
preserve the aspect ratio of the data. Four values may be given, in the order:
bottom, right, top, left. If fewer than four values are given, extra values are
used equal to the first supplied value. If these margins are too narrow any
axis annotation may be clipped. If a null (!
) value is supplied, the value
used is (for all edges); 0.15
if annotated axes are being produced; 0.04, if a
simple border is being produced; and 0.0 if neither border nor axes are being
produced. [
current value]
The method by which the
maximum and minimum data values to be displayed are chosen. The options are as
follows.
-
"Current"
–- The image is scaled between the upper and lower limits that were used by
the previous invocation of DISPLAY. If the previous scaling limits cannot be
determined, the MODE value reverts to "Scale"
.
-
"Faint"
–- The image is scaled between the mean data value minus one standard deviation
and the mean data value plus seven standard deviations. The scaling values are reported
so that the faster Scale mode may be utilised later.
-
"Flash"
–- The image is flashed on to the screen without any scaling at all. This is
the fastest option.
-
"Percentiles"
–- The image is scaled between the data values corresponding to two
percentiles. The scaling values are reported so that the faster Scale mode may be used
later.
-
"Range"
–- The image is scaled between the minimum and maximum data values.
-
"Scale"
–- You define the upper and lower limits between which the image is to be
scaled. The application reports the maximum and the minimum data values for reference
and makes these the suggested defaults.
-
"Sigmas"
–- The image is scaled between two standard-deviation limits. The scaling
values used are reported so that the faster Scale mode may be utilised later.
NN =
_LOGICAL (Read)
If TRUE
the input lookup table is mapped to the colour table by using
the nearest-neighbour method. This preserves sharp edges and is better for lookup
tables with blocks of colour. If NN is FALSE
, linear interpolation is used, and this
is suitable for smoothly varying colour tables. NN is ignored unless LUT is
not null. [FALSE]
NUMBIN = _INTEGER (Read)
The number of histogram bins
used to compute percentiles for scaling. (Percentiles mode) [2048]
OUT =
NDF (Write)
A scaled copy of the displayed section of the image. Values in
this output image are integer colour indices shifted to exclude the indices
reserved for the palette (i.e. the value zero refers to the first colour index
following the palette). The output NDF is intended to be used as the input data in
conjunction with SCALE=FALSE
. If a null value (!
) is supplied, no output NDF will be
created. This parameter is not accessed when SCALE=FALSE
. [!]
PENRANGE( 2 )
= _REAL (Read)
The range of colour indices (“pens”) to use. The supplied
values are fractional values where zero corresponds to the lowest available
colour index and 1.0 corresponds to the highest available colour index. The
default value of [0.0,1.0]
thus causes the full range of colour indices to
be used. Note, if Parameter LUT is null (!) or Parameter SCALE is FALSE
then
this parameter is ignored and the fill range of pens is used. [0.0,1.0]
PERCENTILES( 2 ) = _REAL (Read)
The percentiles that define the scaling limits. For
example, [25,75]
would scale between the quartile values. (Percentile mode)
SCALE = _LOGICAL (Read)
If TRUE
the input data are to be scaled according to
the value of Parameter MODE. If it is FALSE
, MODE is ignored, and the input
data are displayed as is (i.e. the data values are simply converted to integer
type and used as indices into the colour table). A value of zero refers to the
first pen following the palette. A FALSE
value is intended to be used with data
previously scaled by this or similar applications which have already performed the
required scaling (see Parameter OUT). It provides the quickest method of image
display within this application. [TRUE]
SIGMAS( 2 ) = _REAL (Read)
The
standard-deviation bounds that define the scaling limits. To obtain values
either side of the mean both a negative and a positive value are required.
Thus [-2,3]
would scale between the mean minus two and the mean plus three
standard deviations. [3,-2]
would give the negative of that.
SQRPIX = _LOGICAL
(Read)
If TRUE
, then the default value for YMAGN equals the value supplied
for XMAGN, resulting in all pixels being displayed as squares on the display
surface. If a FALSE
value is supplied for SQRPIX, then the default value for
YMAGN is chosen to retain the pixels original aspect ratio at the centre of the
image. [
current value]
STYLE = GROUP (Read)
A group of attribute settings
describing the plotting style to use for the annotated axes (see Parameter
AXES).
A comma-separated list of strings should be given in which each string is either an
attribute setting, or the name of a text file preceded by an up-arrow character
""
.
Such text files should contain further comma-separated lists which will be read and
interpreted in the same manner. Attribute settings are applied in the order in which
they occur within the list, with later settings overriding any earlier settings given
for the same attribute.
Each individual attribute setting should be of the form:
name=value
where name
is the name of a plotting attribute, and
value
is the value to assign to the attribute. Default values will be used for any
unspecified attributes. All attributes will be defaulted if a null value (!
)–-the
initial default–-is supplied. To apply changes of style to only the current invocation,
begin these attributes with a plus sign. A mixture of persistent and temporary style
changes is achieved by listing all the persistent attributes followed by a plus sign
then the list of temporary attributes.
See Section E for a description of the available attributes. Any unrecognised
attributes are ignored (no error is reported). [
current value]
USEAXIS = GROUP
(Read)
USEAXIS is only accessed if the current co-ordinate Frame of the NDF has more
than two axes. A group of two strings should be supplied specifying the two axes
which are to be used when annotating the image, and when supplying a value
for Parameter CENTRE. Each axis can be specified using one of the following
options.
-
Its integer index within the current Frame of the input NDF (in the range 1 to the
number of axes in the current Frame).
-
Its Symbol string such as "RA"
or "VRAD"
.
-
A generic option where "SPEC"
requests the spectral axis, "TIME"
selects the time axis,
"SKYLON"
and "SKYLAT"
picks the sky longitude and latitude axes respectively. Only
those axis domains present are available as options.
A list of acceptable values is displayed if an illegal value is supplied. If a null (!
)
value is supplied, the axes with the same indices as the two used pixel axes within
the NDF are used. [!]
XMAGN = _REAL (Read)
The horizontal magnification
for the image. The default value of 1.0
corresponds to ’normal’ magnification
in which the the image fills the available space in at least one dimension.
A value larger than 1.0 makes each data pixel wider. If this results in the
image being wider than the available space then the image will be clipped to
display fewer pixels. See also Parameters YMAGN, CENTRE, SQRPIX, and FILL.
[1.0]
YMAGN = _REAL (Read)
The vertical magnification for the image. A
value of
1.0
corresponds to ’normal’ magnification in which the image fills
the available space in at least one dimension. A value larger than 1.0 makes
each data pixel taller. If this results in the image being taller than the
available space then the image will be clipped to display fewer pixels. See
also Parameters XMAGN, CENTRE, and FILL. If a null ((
!
) value is supplied,
the default value used depends on Parameter SQRPIX. If SQRPIX is
TRUE
, the
default YMAGN value used is the value supplied for XMAGN. This will result in
each pixel occupying a square area on the screen. If SQRPIX is
FALSE
, then the
default value for YMAGN is chosen so that each pixel occupies a rectangular
area on the screen matching the pixel aspect ratio at the centre of the image,
determined within the
current WCS Frame. [!]