Index: /branches/ipp-magic-v0/psLib/src/imageops/psImageCovariance.h
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--- /branches/ipp-magic-v0/psLib/src/imageops/psImageCovariance.h	(revision 21317)
+++ /branches/ipp-magic-v0/psLib/src/imageops/psImageCovariance.h	(revision 21317)
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+/* @file psImageCovariance.h
+ *
+ * @brief Calculations involving image covariance
+ *
+ * @author Paul Price, IfA
+ *
+ * @version $Revision: 1.4 $ $Name: not supported by cvs2svn $
+ * @date $Date: 2009-02-05 20:15:32 $
+ * Copyright 2009 Institute for Astronomy, University of Hawaii
+ */
+
+#ifndef PS_IMAGE_COVARIANCE_H
+#define PS_IMAGE_COVARIANCE_H
+
+/// @addtogroup ImageOps Image Operations
+/// @{
+
+#include <psImageConvolve.h>
+
+// We don't carry the entire covariance matrix for an image (the size goes as N^2, for N pixels, which makes
+// storage difficult; and if that's not enough, the time to do the calculation is definitely impractical).
+// Since there are (generally) lots of zeros in the covariance matrix, and the same basic pattern repeats (for
+// background pixels), we can just carry that pattern ("covariance pseudo-matrix").  We carry this in a
+// psKernel, since the values are the covariance between the pixel of consideration (at 0,0 in the kernel) and
+// neighbouring pixels.  Note that this may not be strictly correct near sources, but this is the best we can
+// do (and much better than most currently do).
+
+/// Allocate a covariance pseudo-matrix with no covariance
+psKernel *psImageCovarianceNone(void);
+
+/// Calculate the covariance pseudo-matrix for a convolution kernel
+psKernel *psImageCovarianceCalculate(
+    const psKernel *kernel,             ///< Convolution kernel
+    const psKernel *covariance          ///< Current covariance pseudo-matrix
+    );
+
+/// Return the pixel-to-pixel covariance factor
+float psImageCovarianceFactor(
+    const psKernel *covariance          ///< Covariance pseudo-matrix
+    );
+
+/// Sum multiple covariance pseudo-matrices
+psKernel *psImageCovarianceSum(
+    const psArray *array                ///< Array of covariance pseudo-matrices
+    );
+
+/// Average multiple covariance pseudo-matrices
+psKernel *psImageCovarianceAverage(
+    const psArray *array                ///< Array of covariance pseudo-matrices
+    );
+
+/// Truncate covariance pseudo-matrix
+///
+/// The covariance pseudo-matrix is truncated by removing the outer regions that contribute less than the
+/// nominated fraction of the total.
+psKernel *psImageCovarianceTruncate(
+    const psKernel *covar,              ///< Covariance pseudo-matrix
+    float frac                          ///< Fraction of covariance to truncate
+    );
+
+/// @}
+#endif // #ifndef PS_IMAGE_COVARIANCE_H