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diff --git a/pkg/images/imfit/doc/imsurfit.hlp b/pkg/images/imfit/doc/imsurfit.hlp new file mode 100644 index 00000000..0aa46a97 --- /dev/null +++ b/pkg/images/imfit/doc/imsurfit.hlp @@ -0,0 +1,226 @@ +.help imsurfit Feb88 images.imfit +.ih +NAME +imsurfit -- fit a surface function to an image +.ih +USAGE +imsurfit input, output, xorder, yorder +.ih +PARAMETERS +.ls input +List of images to be fit. +.le +.ls output +Output image(s) of \fItype_output\fR. +.le +.ls xorder +The order in x of the polynomials (1 = constant) or the number of polynomial +pieces for the bicubic spline. +.le +.ls yorder +The order in y of the polynomials (1 = constant) or the number of polynomial +pieces for the bicubic spline. +.le +.ls cross_terms = yes +Cross terms for the polynomials. For example, if \fIxorder\fR = 2 and +\fIyorder\fR = 2 +then a function of the form z = a + b * x + c * y + d * x * y will be fit. +.le +.ls function = "leg" +Functional for of surface to be fit to the image. The available functions +(with minimum match abbreviation) are: +.ls legendre +.le +.ls chebyshev +.le +.ls spline3 +.le +.ls spline1 +.le +.le +.ls type_output = "fit" +The type of output image. The allowed types (with minimum match abbreviation) +are: +.ls clean +The input image with deviant pixels in the good regions replaced by the +fitted value. +.le +.ls fit +An image created from the surface fits to the image. +.le +.ls residual +The difference of the input image and the fitted image. +.le +.ls response +The ratio of the input image to the fitted image. +All fitted (denominator) pixels below \fIdiv_min\fR are given a value of 1. +.le +.le +.ls xmedian = 1, ymedian = 1 +The x and y dimensions of the box used for median processing. +If \fIxmedian\fR > 1 or \fIymedian\fR is > 1, +then the median is calculated for each box and used in the surface +fit instead of the individual pixels. +.le +.ls median_percent = 50. +If the number of pixels in the median box is less than \fImedian_percent\fR * +\fIxmedian\fR * \fIymedian\fR the box will be omitted from the fit. +.le +.ls upper = 0., lower = 0. +The number of sigma limits for pixel rejection. If \fIupper\fR > 0. or +\fIlower\fR > 0. and median processing is turned off, +pixel rejection is enabled. +.le +.ls ngrow = 0 +The radius in pixels for region growing. +Pixels within a distance of \fIngrow\fR pixels of +a rejected pixel are also rejected. +.le +.ls niter = 0 +The maximum number of iterations in the rejection cycle. +Rejection will be terminated if the number of rejected pixels is zero +or the number of iterations equals \fIniter\fR. +.le +.ls regions = "all" +The available options (with minimum match abbreviation) are: +.ls all +All points in the image are fit. +.le +.ls rows +The fit is performed on the image rows specified by \fIrows\fR. +.le +.ls columns +The fit is performed on the image columns specified by \fIcolumns\fR. +.le +.ls border +The fit is performed on a border around the image whose width is specified +by \fIborder\fR. +.le +.ls sections +The fit is performed on image sections listed in the file specified +by \fIsections\fR. +.le +.ls circle +The fit is performed on a circular region whose parameters are specified by +\fIcircle\fR. +.le +.ls invcircle +The fit is performed on a region exterior to the circular region whose +parameters are specified by \fIcircle\fR. +.le +.le +.ls rows = "*" +When \fIregion_type\fR = 'rows', the string parameter \fIrows\fR specifies +the rows to be fit. +.le +.ls columns = "*" +When \fIregion_type\fR = 'columns', the string parameter \fIcolumns\fR +specifies the columns to be fit. +.le +.ls border = "50" +When \fIregion_type\fR = 'border', the +string parameter \fIborder\fR specifies the width of the border to be fit. +.le +.ls sections = "" +When \fIregion_type\fR = 'sections', the +string parameter \fIsections\fR is the name of the file containing the list of +image sections to be fit, where \fISections\fR may be the standard +input (STDIN). +The sections must be listed one per line in the following form: x1 x2 y1 y2. +.le +.ls circle = "" +The string parameter \fIcircle\fR lists the parameter needed to specify +the circle in the following format: xcenter ycenter radius. The three +parameters must be integers. +.le +.ls div_min = INDEF +When \fItype_output\fR = 'response' all divisions in which the fitted value +is below \fIdiv_min\fR are set to the value 1. +.le +.ih +DESCRIPTION +A surface is fit to selected portions of the input image. +The user may elect to fit the whole image, \fIregion_type\fR = 'all', +selected rows, \fIregion_type\fR = 'rows', selected columns, +\fIregion_type\fR = 'columns', a +border around the image, \fIregion_type\fR = 'border' or image sections, +\fIregion_type\fR = 'sections'. If the sections option is enabled the user +must supply the name of the file containing a list of sections, +\fIsections\fR = 'list', or enter them from the standard input. In either case +the sections must be listed one per line in the following form: x1 x2 y1 y2. + +The parameter \fIsurface_type\fR may be a +"legendre" polynomial, "chebyshev" polynomial, +a cubic spline ("spline3") or a linear spline ("spline1"). +The order of the polynomials is selected in both x and y. +Cross terms for the polynomial surfaces are optional. +For the cubic spline the parameters \fIxorder\fR and \fIyorder\fR specify +the number of polynomial pieces to be fit to the surface in +each direction. + +The output image may be the fitted image, the difference between the +input and the fitted image, the ratio of the input to the fitted image +or the input image with deviant pixels in the fitted regions replaced +with the fitted values, according to whether \fItype_output\fR = +'fit', 'residual', +'response' or 'clean'. If \fItype_output\fR = 'response' then pixels in the +fitted image with values < \fIdiv_min\fR are replaced by 1. +If \fItype_output\fR = +'clean' then at least one of \fIupper\fR or \fIlower\fR must be > 0. + +Pixel rejection is enabled if median processing is turned off, +\fIniter\fR > 0, +and at least one of the parameters \fIupper\fR and \fIlower\fR is > 0. +Region growing +can be turned on by setting \fIngrow\fR > 0, in which case all pixels within +a radius ngrow of a deviant pixel will be rejected. + +.ih +EXAMPLES +1. To create a smoothed version of an image: + +.nf + cl> imsurfit m74 m74smooth 5 10 function=spline3 +.fi + +2. To create a smoothed version of an image using median processing: + +.nf + cl> imsurfit m74 m74med 5 10 function=spline3 \ + >>> xmed=5 ymed=5 +.fi + +3. To subtract a constant background from an image: + +.nf + cl> imsurfit abell30 abell30bck 1 1 function=leg \ + >>> type=resid +.fi + +4. To make a ratio image using signals above 1000 units: + +.nf + cl> imsurfit n7006 n7006ratio 20 20 function=spline3 \ + >>> type=response div_min=1000 +.fi + +.ih +TIMINGS +Fitting and subtracting a constant from a 512 by 512 IRAF image requires +~35 cpu seconds. Approximately 130 cpu seconds are required to fit a +second degree polynomial in x and y (including cross-terms) to a +100 pixel wide border around a 512 by +512 IRAF image, and to subtract the fitted image from the input image. +To produce a smooth 512 by 512 IRAF image using a 10 by 10 bicubic spline +requires ~300 cpu seconds. Timings refer to a VAX 11/750 + fpa. + +.ih +NOTES +The surface fitting code uses the IRAF SURFIT math routines, +which have been optimized for image fitting . +The routines which fit selected portions +of the image, perform pixel rejection and region growing, and create and +maintain a list of rejected pixels utilize the ranges and pixlist packages +of routines currently maintained in the images directory. These will be +replaced by more general ranges and image masking routines in the future. +.endhelp |