AIPS HELP file for IMEAN in 31DEC20
As of Mon Sep 21 11:02:41 2020
IMEAN: Task to print the mean, rms and extrema in an image
DOHIST -3.0 2.01 True (1.0) do histogram plot.
= 2 => flux on x axis
USERID -32000.0 32000.0 User ID. ignored
INNAME Image name (name)
INCLASS Image name (class)
INSEQ 0.0 9999.0 Image name (seq. #)
INDISK 0.0 9.0 Disk drive #
BLC -1.0 4096.0 Bottom left corner of image
TRC 0.0 4096.0 Top right corner of image
DOINVERS -1.0 1.0 > 0 => histogram outside
<=0 => inside BLC/TRC
NBOXES 0.0 1024.0 No. of ranges for histogram.
PIXRANGE Min and max range for hist.
FUNCTYPE 'LG' => do log10 plot of #
samples, else linear
DOMODEL -1.0 1.0 > 0 fit, plot Gaussian
DOCAT -1.0 3.0 Put true RMS in header
>= 2 even for amall subimg.
LTYPE -410.0 410.0 Type of labeling: 1 border,
2 no ticks, 3 - 6 standard,
7 - 10 only tick labels
<0 -> no date/time
DOPRINT 0 - no print, -3 brief
OUTTEXT Name of output log file,
No output to file if blank
DOTV -1.0 1.0 > 0 Do plot on the TV, else
make a plot file
GRCHAN 0.0 8.0 Graphics channel 0 => 1.
PIXAVG @ Mean noise value
PIXSTD @ True noise rms
TRIANGLE @ Brightness at the top 1 percent, 2 percent,
@ 3 percent, ,,,50 percent of full histogram
Use: IMEAN will read a portion of an image and print the mean and rms
brightnesses found. It also prints the location and value of the
max and min brightnesses in that portion. For clean maps, the
mean is converted into a total flux. An option to generate a
histogram plot and/or print file is available. It also computes
the peak and rms of the histogram of the image in an attempt to
determine the mean and rms of the noise part of the signal. It
determines the initial values for this from the header
(ACTNOISE, ACTMEAN) or from a robust fit from the first plane of
the image. Note that pixel values which are exactly zero are
not used in the fit for the rms. This allows blanked pixels to
be REMAGed to zero without affecting these computations.
Three adverbs are returned by the task. This allows the fit
mean and noise to be used in other computations or tasks. It
also returns in TRIANGLE(i) the brightness level exceeded by i percent
of the pixels.
The aperture for the computation may be either rectangular or
The histogram is computed even if it will not be plotted since
it may be printed. Thus, BLC, TRC, DOINVERS, NBOXES, PIXRANGE
are used even of DOHIST <= 0.
A special one-line print option is available when DOPRINT=-3.
DOHIST......True (>0) means plot the histogram determined with
NBOXES and PIXRANGE. A second histogram is always
computed, ignoring these adverbs, in an attempt to fit a
Gaussian to the peak. If that is succesful, the fit is
plotted on any plotted histogram. If 0 < DOHIST <= 1,
then the flux is plotted on the Y axis and the counts on
the X axis. If DOHIST > 1, the axes are reversed -
which is a more common form.
USERID......User ID of owner of image. Ignored.
INNAME......Image name(name). Standard defaults.
INCLASS.....Image name(class). Standard defaults.
INSEQ.......Image name(seq. #). 0 => highest.
INDISK......Disk drive # of image. 0 => any.
BLC.........The Bottom Left-hand pixel of the subarray of the image to
be analysed. The value (0,0) means (1,1).
If BLC(1) = -1, then BLC(2) is taken as the radius of a
circular aperture centered in TRC(1),TRC(2) which must
be specified, not defaulted.
TRC.........The Top Right-hand pixel of the subarray of the image to
be analysed. The value (0,0) means the top right hand
corner of the entire image.
See note about circular aperture under BLC above.
DOINVERS....> 0 Do the histogram OUTSIDE the rectangular or
circular area defined by BLC/TRC
<= 0 Do the histogram INSIDE (including borders) the
rectangular or circular area defined by BLC/TRC
NBOXES......Number of boxes used in computing histogram for
plotting. The number of boxes used to compute the
apparent noise rms is controlled by the task.
<= 1 => 101 boxes, > 1024 => 512
PIXRANGE....Intensity range min/max over which plotted histogram is
computed. Max <= min (i.e. 0) => full range. This is
used to set the range between the center of box 1 and
the center of box NBOXES.
FUNCTYPE....Type of axis plot for number of samples in each box. 'LG'
=> log base 10, else linear.
DOMODEL.....> 0 => fit a Gaussian to the histogram and plot it along
with the histogram.
DOCAT.......> 0 => write the new actual noise estimate as keyword
ACTNOISE and the estimate zero level as ACTMEAN in the
image header. If BLC/TRC occupies less than 20 percent of a
plane or less than 10 percent of a cube, this function will be
done only if DOCAT >= 2.
LTYPE.......Labelling type, see HELP LTYPE for details:
1 = border, 2 = no ticks, 3 or 7 = standard, 4 or 8 =
relative to ref. pixel, 5 or 9 = relative to subimage
(BLC, TRC) center, 6 or 10 = pixels. 7-10 all labels
other than tick numbers and axis type are omitted.
Less than 0 is the same except that the plot file
version number and create time are omitted.
Add n * 100 to alter the metric scaling.
DOPRINT.....Additional print control when OUTTEXT is not blank.
= 0 => no printing, = -3 => print a single line giving
BLC(3-7), TRC(3-7), minimum, maximum, flux, and rms all
in one line. For plots note that task RSPEC will
compute rmses and plot the spectra (and print it too).
OUTTEXT.....Output file to log measurements for later user processing.
File created if it does not exist and appended to if it
already exists. Nothing is written to a file if the
name is blank. File name should contain directory and
file parts, i.e, "LOCAL:IMEAN.OUT" or
"RUNFIL:IMPORTANT.POINTS". The histogram is printed into
the file even if DOHIST <= 0.
DOTV........> 0 => plot directly on the TV device, otherwise make a
plot file for later display on one or more devices
(including the TV if desired).
GRCHAN......Graphics channel (1 - 7) to use for line drawing. 0 => 1
PIXAVG......Mean value of the noise part of the image. The final
fit to the noise portion is returned.
PIXSTD......RMS of the noise portion of the image. The final fit is
TRIANGLE....TRIANGLE(i) returns the brightness which is exceeded by
only i percent of the pixels. Values for 1 to 50 percent are
returned. Note that the histoigram used to compute this
is computed over the full intensity range of the image,
not just PIXRANGE.