Changeset 1113 for trunk/doc/modules/ModulesSDRS.tex

Timestamp:

Jun 28, 2004, 3:44:33 PM (22 years ago)

Author:

Paul Price

Message:

Hacked sky subtraction.

File:

• trunk/doc/modules/ModulesSDRS.tex (modified) (7 diffs)

trunk/doc/modules/ModulesSDRS.tex

@@ -1 @@
-%%% $Id: ModulesSDRS.tex,v 1.4 2004-06-26 03:42:48 price Exp $
+%%% $Id: ModulesSDRS.tex,v 1.5 2004-06-29 01:44:23 price Exp $
 \documentclass[panstarrs]{panstarrs}
 
@@ -294 +294 @@
 
 \subsection{Bias subtraction}
+\label{sec:bias}
 
 Given an input image and various other parameters,
@@ -299 +300 @@
 The API shall be the following:
 \begin{verbatim}
-psReadout *psPhase2SubtractBias(psReadout *in, void *fitSpec, psOverscanAxis overscanAxis, psBiasFit fit,
+psReadout *psPhase2SubtractBias(psReadout *in, void *fitSpec, psOverscanAxis overscanAxis, psFit fit,
                                 int nBin, const psList *regions, const psStats *stat, const psImage *bias);
 \end{verbatim}
@@ -310 +311 @@
 
 \begin{verbatim}
-/** Fit type for bias */
+/** Fit type */
 typedef enum {
-    PS_OVERSCAN_FIT_NONE,               ///< No fit to bias
-    PS_OVERSCAN_FIT_LINEAR,             ///< Do linear interpolation on bias
-    PS_OVERSCAN_FIT_POLYNOMIAL,         ///< Fit polynomial to bias
-    PS_OVERSCAN_FIT_CHEBYSHEV,          ///< Fit chebyshev to bias
-    PS_OVERSCAN_FIT_SPLINE              ///< Fit cubic splines to bias
-} psBiasFit;
-\end{verbatim}
-
-If \code{fitSpec} is \code{NULL}, or \code{fit} is
-\code{PS_OVERSCAN_FIT_NONE}, then no fit shall be performed to the
-overscan.  If \code{fit} is \code{PS_OVERSCAN_FIT_LINEAR}, then the
-function shall perform simple linear interpolation between points in
-the overscan.  Otherwise, \code{fitSpec} shall be interpreted to be a
-structure of the appropriate type (\code{psPolynomial1D} for
-\code{PS_OVERSCAN_FIT_POLYNOMIAL} and
-\code{PS_OVERSCAN_FIT_CHEBYSHEV}, and \code{psSpline1D} for
-\code{PS_OVERSCAN_FIT_SPLINE}), and the overscan shall be fit using
-the specified functional form.  Upon return, the \code{fitSpec} shall
+    PS_FIT_NONE,                ///< No fit
+    PS_FIT_LINEAR,              ///< Do linear interpolation
+    PS_FIT_POLYNOMIAL,          ///< Fit polynomial
+    PS_FIT_CHEBYSHEV,           ///< Fit chebyshev
+    PS_FIT_SPLINE               ///< Fit cubic splines
+} psFit;
+\end{verbatim}
+
+If \code{fitSpec} is \code{NULL}, or \code{fit} is \code{PS_FIT_NONE},
+then no fit shall be performed to the overscan.  If \code{fit} is
+\code{PS_FIT_LINEAR}, then the function shall perform simple linear
+interpolation between points in the overscan.  Otherwise,
+\code{fitSpec} shall be interpreted to be a structure of the
+appropriate type (\code{psPolynomial1D} for \code{PS_FIT_POLYNOMIAL}
+and \code{PS_FIT_CHEBYSHEV}, and \code{psSpline1D} for
+\code{PS_FIT_SPLINE}), and the overscan shall be fit using the
+specified functional form.  Upon return, the \code{fitSpec} shall
 contain the coefficients of the overscan fit.
 
@@ -351 +351 @@
 warning shall be generated if the \code{overscanAxis} is
 \code{PS_OVERSCAN_NONE} or \code{PS_OVERSCAN_ALL} and the \code{fit}
-is not \code{PS_OVERSCAN_FIT_NONE}.
+is not \code{PS_FIT_NONE}.
 
 If the \code{overscanAxis} is \code{PS_OVERSCAN_ROWS} or
@@ -361 +361 @@
 If the overscan is not defined for each row/column, then the function
 shall generate a warning and then interpolate using the provided
-functional form if \code{fit} is not \code{PS_OVERSCAN_FIT_NONE};
+functional form if \code{fit} is not \code{PS_FIT_NONE};
 otherwise, the function shall generate an error.
 
@@ -484 +484 @@
 \subsection{Subtract sky}
 
-Given an input image, a polynomial specifying the order of a desired
-fit, a list of template background images, a list of catalog stars on
-or near the chip, and parameters specifying how to grow the radius of
-the objects, and the binning factor, \code{psPhase2SubtractSky} shall
-fit and subtract the background of the image.  The API shall be the
-following:
-\begin{verbatim}
-/** Subtracts the sky background. */
+\tbd{This is a simply sky subtraction routine.  A more complicated
+routine will be specified in the future, following research into the
+best algorithm.}
+
+Given an input image, a polynomial or spline specifying the order of a
+desired fit, a binning factor and statistics to use for the binning,
+along with a clipping level, \code{psPhase2SubtractSky} shall fit and
+subtract a model for the background of the image.  The API shall be
+the following:
+\begin{verbatim}
+/** Simple sky subtraction */
 psReadout *psPhase2SubtractSky(psReadout *in, ///< Input image to be sky-subtracted, and output
-                               psPolynomial2D *poly, ///< Polynomial specification, returns coeffcients
-                               psVector *outNorms, ///< Normalisations of the template sky images: output
-                               const psList *skyImages, ///< Template sky images: a list of type psImage, or
-                                                        ///< NULL
-                               const psList *catalog, ///< Sources nearby to mask when measuring the
-                                                      ///< background: a list of type psObject, or NULL
-                               float radiusMultiply, ///< Multiplying factor of object radius for mask
-                               float radiusAdd, ///< Additive factor to grow the object masks
-                               int binFactor ///< Binning factor to use on image before solving for polynomial
-                               );
-\end{verbatim}
-
-The polynomial specification, \code{poly}, specifies the order of the
-polynomial to be used in fitting the background.  Note that the input
-image, \code{in}, shall be subtracted in-place.  The function shall
-return the subtracted image, and also update the polynomial,
-\code{poly}, to hold the polynomial coefficients used in the
-subtraction, and update the vector \code{outNorms} to hold the
-normalisations of each of the template background images used in the
-subtraction.  The \code{outNorms} vector shall be resized if necessary
-to match the number of template sky images in the list
-\code{skyImages}.  If the polynomial specification is \code{NULL}, then
-no polynomial shall be fit to the input image.
-
-Note that the input image, \code{in}, and the template sky images,
-\code{skyImages}, need not be the same size, since the input image may
-already have been trimmed (following overscan subtraction), but the
-function shall use the offsets in the image (\code{in->x0} and
-\code{in->y0}) to determine the appropriate offsets to obtain the
-correct pixels.  In the event that one (or more) of the
-\code{skyImages} is too small (i.e., pixels on the input image refer
-to pixels outside the range of the \code{skyImages} image), the
-function shall generate an error.
-
-The \code{catalog} shall be a linked list of \code{psObject} which
-corresponds to objects on the input image.  If the size of a source in
-the \code{catalog} is \code{size}, then the radius to mask around the
-source before fitting the background shall be \code{radiusMultiply}
-$\times$ \code{size} + \code{radiusAdd}.
-
-\tbd{Are the catalog stars in celestial or pixel coordinates?  I lean
-to pixel coordinates.}
-
-\tbd{What size do we use?  FWHM?}
-
-When fitting a polynomial, the function shall bin the input image by
-\code{binFactor} in order to reduce the required processing time.
-
-\code{poly} may be \code{NULL} in order to specify that only the
-template sky images should be used in the fitting, and no polynomial
-terms.  \code{outNorms} may be \code{NULL} if the caller is not
-interested in the normalisations.  \code{skyImages} may be \code{NULL}
-in order to specify that there are no input sky template images.
-\code{catalog} may be \code{NULL} in order to specify that there are
-no objects to mask.  If both \code{poly} and \code{skyImages} are
-\code{NULL}, then the function shall simply return the input image
-with no processing.
+                               void *fitSpec, ///< Polynomial/Spline specification, returns coeffcients
+                               psFit fit, ///< Fit type
+                               int binFactor, ///< Binning factor to use on image before solving for polynomial
+                               psStats *stats, ///< Statistics to use in binning
+                               float clipSD ///< Standard deviations to clip at after binning.
+                               );
+\end{verbatim}
+
+Note that the input image, \code{in}, shall be subtracted in-place.
+The function shall return the subtracted image, and also update the
+polynomial, chebyshev or spline specified by \code{fitSpec}, to hold
+the coefficients used in the subtraction.
+
+The fit specification, \code{fitSpec}, specifies the order of the
+polynomial or spline to be used in fitting the background.
+\code{fitSpec} shall be interpreted as a polynomial, Chebyshev or
+spline on the basis of \code{fit} (in the same manner as for bias
+subtraction; \S\ref{sec:bias}).  If \code{fitSpec} is \code{NULL} or
+\code{fit} is \code{PS_FIT_NONE}, then no fit shall be performed, and
+the function shall simply return.
+
+When fitting the polynomial, the function shall first bin the input
+image by \code{binFactor} in order to reduce the required processing
+time.  The statistic to use in this binning is specified by
+\code{stat}.  \code{stat} is of type \code{psStats} instead of simply
+\code{psStatsOptions} so that clipping levels may be specified, if
+desired.  In the event that multiple options are specified by
+\code{stats}, a warning shall be generated, and the option with the
+highest priority shall be used, according to the following priority
+order: \code{PS_STAT_SAMPLE_MEAN}, \code{PS_STAT_SAMPLE_MEDIAN},
+\code{PS_STAT_CLIPPED_MEAN}, \code{PS_STAT_ROBUST_MEAN},\
+\code{PS_STAT_ROBUST_MEDIAN}, \code{PS_STAT_ROBUST_MODE}.  If the
+\code{binFactor} is non-positive, or \code{stats} is \code{NULL} or
+fails to specify an option, a warning shall be generated, and the fit
+shall be performed on the entire image.
+
+Binned pixels deviating more than \code{clipSD} standard deviations
+from the mean of the binned pixels shall be clipped in a single
+clipping iteration.  If the \code{clipSD} is non-positive, then the
+function shall generate a warning and not perform any clipping.
+
 
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