Program: DECIM
Purpose: Decrease size of a set in any direction with an
integer factor
Category: MANIPULATION, CALCULATION
File: decim.c
Author: M. Vogelaar
Keywords:
INSET= Give set (, subsets) to decimate:
Maximum number of subsets is 2048.
BOX= Frame for input subsets. [entire subset]
DECIM= Give decimation: [1,...]
The user can specify a decimation factor for each axis
in a subset. The default value for each axis is 1.
Negative values are not allowed.
** SHIFT= Shift in start of decimation: [0]
Specify which of the 'decim' number of pixels
will be transferred to the new created output pixel.
If for example a decimation factor 3 is specified, the
pixels 0, 1, 2 create a new output pixel containing the
value of the original pixel 0 by default. However, if
the user wants to transfer one of the other pixels,
he has to specify a shift. For the decimation factor 3
the shifts 1 and 2 are allowed. Of negative shifts, the
absolute values are taken and of shift values greater
than (decimation - 1) the modulus is calculated.
OUTSET= Give output set (, subsets):
Output set and subset(s) for the result. The number of
output subsets is the same as the number of input sub-
sets.
Description: Decimate data in each specified direction of a subset.
The decimation factor must be an integer number.
In the output, pixel 0 will always be retained.
If for example the user specified the decimation factor
3, then the pixels -9, -6, -3, 0, 3, 6, 9 etc. will be
in the output. If he also specified for this axis a
shift of 1, the pixels -5, -2, 1, 4, 7 etc. will be
transferred. A possible use of the shift could be the
creation of sets made with different shifts to combine
them to a new set with flux that can be compared to
the flux of the original (not decimated) set.
Example:
Updates: ... .., 1990: VOG, Document created.
jun 11, 1996: VOG, Bug in output size removed.
Oct 1, 1996: VOG, DECIM could not handle subsets:
out=0 initialisation was move from
outside to inside subset loop.