NAME

flagflat -- Flag WF/PC flat field pixels which are abnormally higher or lower than the local average value.

USAGE

flagflat infile inmask outmask boxsize sigma

DESCRIPTION

This task searches for pixels which are abnormally higher or lower than the average value of their neighboring pixels. The corresponding data quality pixels will be flagged as defective. This task is useful to mask protruding features in a flat field file. The following steps are used in this task:

(1) Using a square box of user-specified size, take the mean of all pixels in this box. Pixels flagged as bad in the input data quality file are not included.

(2) Pixel values larger than the upper limit (= mean times the factor as specified in the parameter "sigma") or smaller than the lower limit (=mean divided by sigma) are marked by assign their corresponding pixels in the output data quality file a "bad mask" value.

(3) Start the above steps from the lower left corner, repeat it by moving the box to the right, one column at a time, until it reaches the right boundary.

(4) Repeat the above steps by moving the box upward, one row at a time, until it reaches the upper boundary.

PARAMETERS

infile = "" [string]

Name of the input file template. Input files must be two-dimensional and REAL data type.

inmask = "" [string]

Name of the input data quality file template. Input data quality file must be 2-D and SHORT data type. Each input file should have one corresponding data quality file.

outmask = "" [string]

Name of the output data quality file template. Each output file should have one corresponding output data quality file. If the the value of this parameter is NULL, the input mask will be updated.

boxsize = [integer, min = 1]

Number of pixels on each side of the averaging box.

sigma = 2. [real, min = 1.]

The factor used to exclude pixels with abnormally high or low flat field value.

EXAMPLES

1. Flag flat field pixels which are higher than twice or less than half of the local average in the file in.r6h. Use an area of 10x10 pixels around each pixel to calculate the local average.

w_> flagflat in.r6h in.b6h new.b6h boxsize=10 sigma=2.

REFERENCE

BUGS

SEE ALSO