; IMFLT ;--------------------------------------------------------------- ;! fits and removes a background intensity plane from an image ;# Task Optical ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 1998 ;; Associated Universities, Inc. Washington DC, USA. ;; ;; This program is free software; you can redistribute it and/or ;; modify it under the terms of the GNU General Public License as ;; published by the Free Software Foundation; either version 2 of ;; the License, or (at your option) any later version. ;; ;; This program is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; ;; You should have received a copy of the GNU General Public ;; License along with this program; if not, write to the Free ;; Software Foundation, Inc., 675 Massachusetts Ave, Cambridge, ;; MA 02139, USA. ;; ;; Correspondence concerning AIPS should be addressed as follows: ;; Internet email: aipsmail@nrao.edu. ;; Postal address: AIPS Project Office ;; National Radio Astronomy Observatory ;; 520 Edgemont Road ;; Charlottesville, VA 22903-2475 USA ;----------------------------------------------------------------------- IMFLT LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC IMFLT Flattens an image by fitting a plane to the image. INNAME Input image name (name) INCLASS Input image name (class) INSEQ 0.0 9999.0 Input image name (seq. #) INDISK 0.0 9.0 Input image disk unit # OUTNAME Output image name (name) OUTCLASS Output image name (class) OUTSEQ -1.0 9999.0 Output image name (seq. #) OUTDISK 0.0 9.0 Output image disk unit #. BLC Bottom left corner of output TRC Top right corner of output NBOXES 0.0 10.0 Number of boxes to include BOX 0.0 4096.0 Four coordinates for each box APARM (1) type of fit (2) direction of fit. PIXRANGE Limit fit to pixels in range ---------------------------------------------------------------- IMFLT Task: Task to read flatten an image by fitting a plane through the data specified in the boxes. If no boxes are specified, the entire map is included in the fit. Adverbs: INNAME.....Input image name (name). Standard defaults. INCLASS....Input image name (class). Standard defaults. INSEQ......Input image name (seq. #). 0 => highest. INDISK.....Disk drive # of input image. 0 => any. OUTNAME....Output image name (name). Standard defaults. OUTCLASS...Output image name (class). Standard defaults. OUTSEQ.....Output image name (seq. #). 0 => highest unique. OUTDISK....Disk drive # of output image. 0 => highest disk number with sufficient space. BLC........Bottom left corner of subimage. 0=> all of axis TRC........Top right corner of subimage. 0=> all of axis NBOXES.....Number of boxes to include in fit to plane BOX........Four coordinates for each box APARM......Specifies the type of fit to perform and fixed parameters. (1) type of fit 0 => subrt. off mean 1 => subrt. off best fit plane -1 => subrt. off constrained plane The constrained plane has maximum slope in the direction APARM(2) measured in degrees CCW from the x-axis. PIXRANGE...Only pixels within PIXR(1) - PIXR(2) are used in the fit. PIXR(1) >= PIXR(2) -> full range. ---------------------------------------------------------------- IMFLT: Task which reads an image file and subtracts a best fit plane to the data. The data included in the fit is determined by the parameters BOX(I,J), J=1, NBOXES where I =1,4 provide BLC and TRC for each box. These parameters are most easilly fit using the verb TVBOX. The type of fit is determined by APARM APARM(1) = 0 => only subtrct off the mean value. = 1 => subtract off the best fit plane. = -1 => subtract off a plane, but constrain the direction of the slope using APARM(2) APARM(2) This is an angle measured in degrees. It specifies which direction in the output map should have zero slope. APARM(2) is only used if APRAM(1) = -1. A future version of IMFLT should allow higher order fits and use APARM(5) and APARM(6) as max and min values for a pixel to be included in the fit. There are two KNOWN problems with this routine, although neither one is a major threat to its usefullness. (1) Not all points included in BOX are used to determine the fit. The image is truncated using BLC and TRC before the fit is determined. (2) If the output image is not flat, because APARM(1) was set to either -1 or 0, there is some ambiguity in determining a mean level for the image. This probably should be the center of the image. Instead, it is the mean position of the pixels included in the fit.