"ORIGIN" — The compression boxes are placed so that the origin of the pixel co-ordinate Frame (i.e.
pixel co-ordinates (0,0)) in the input NDF corresponds to a corner of a compression box.
This results in the pixel origin being retain in the output NDF. For instance, if a pair of
two-dimensional images which have previously been aligned in pixel co-ordinates are compressed,
then using this option ensures that the compressed images will also be aligned in pixel
"FIRST" — The compression boxes are placed so that the first pixel in the input NDF (for instance, the
bottom-left pixel in a two-dimensional image) corresponds to the first pixel in a compression box. This
can result in the pixel origin being shifted by up to one compression box in the output image. Thus,
images which were previously aligned in pixel co-ordinates may not be aligned after compression.
You may want to use this option if you are using a very large box to reduce the number of dimensions
in the data (for instance summing across the entire width of an image to produce a one-dimensional
"LAST" — The compression boxes are placed so that the last pixel in the input NDF (for instance, the
top-right pixel in a two-dimensional image) corresponds to the last pixel in a compression box. See the
"FIRST" option above for further comments.
TRUEthe application forms weighted averages of the axis centres using the variance. For all other conditions the non-bad axis centres are given equal weight during the averaging to form the output axis centres.
TRUEthe output values are normalised: the addition is multiplied by the ratio of the number of pixels in the box to the number of good pixels therein to arrive at the output value. When NORMAL=
FALSEthe output values are always just the sum of the good pixels.
TRUE. However, this may result in overflows for integer types and hence additional bad values written to the output NDF. If this parameter is set
FALSEthen the output data type will be one of _REAL or _DOUBLE, depending on the input type.
!) propagates the title from the input NDF to the output NDF.
TRUE, the output NDF only contains data for compression boxes which are entirely contained within the input NDF. Any pixels around the edge of the input NDF which are not contained within a compression box are ignored. If TRIM is set
FALSE, the output NDF contains data for all compression boxes which have any overlap with the input NDF. All pixels outside the bounds of the NDF are assumed to be bad. That is, any boxes which extend beyond the bounds of the input NDF are padded with bad pixels. See also Parameter ALIGN.
WLIM specifies the minimum fraction of good pixels which must be present in the summation box in
order to generate a good output pixel. If this specified minimum fraction of good input pixels is not
present, then a bad output pixel will result, otherwise the output value will be the sum of
the good values. The value of this parameter should lie between 0.0 and 1.0 (the actual
number used will be rounded up if necessary to correspond to at least one pixel).
"FIRST"so that each compression box is flush with the left edge of the input image. TRIM is set to
NOso that compression boxes which extend outside the bounds of the input image (which will be all of them if the input image is narrower than 10000 pixels) are retained in the output NDF.
The axis centres and variances are averaged, whilst the widths are summed and always normalised for bad values.
This routine correctly processes the AXIS, DATA, VARIANCE, LABEL, TITLE, UNITS, WCS, and HISTORY components of the input NDF and propagates all extensions. QUALITY is not processed since it is a series of flags, not numerical values.
All non-complex numeric data types can be handled.
Any number of NDF dimensions is supported.