CORRMAT_ANALYZE

       Find the optimal (x,y) offset to maximize correlation of 2 images

       Analyzes the 2-D cross-correlation function of two images
       and finds the optimal(x,y) pixel offsets.
       Intended for use with function CORREL_IMAGES.

       corrmat_analyze, correl_mat, xoffset_optimum, yoffset_optimum,
               max_corr, edge, plateau, [XOFF_INIT=, YOFF_INIT=, REDUCTION=,
               MAGNIFICATION=, PLATEAU_THRESH=, /PRINT]

       correl_mat = the cross-correlation matrix of 2 images.
                       (as computed by function CORREL_IMAGES( imA, imB ) ).

       If correl_mat(*,*,1) is the number of pixels for each correlation,
       (the case when /NUMPIX was specified in call to CORREL_IMAGES)
       then sqrt( sqrt( # pixels )) is used as correlation weighting factor.

       XOFF_INIT = initial X pixel offset of image_B relative to image_A.
       YOFF_INIT = Y pixel offset, (both as specified to correl_images).
       REDUCTION = reduction factor used in call to CORREL_IMAGES.
       MAGNIFICATION = magnification factor used in call to CORREL_IMAGES,
               this allows determination of offsets up to fractions of a pixel.
       PLATEAU_THRESH = threshold used for detecting plateaus in
               the cross-correlation matrix near maximum, (default=0.01),
               used only if MAGNIFICATION > 1
       /PRINT causes the result of analysis to be printed.

       xoffset_optimum = optimal X pixel offset of image_B relative to image_A.
       yoffset_optimum = optimal Y pixel offset.
       max_corr = the maximal correlation corresponding to optimal offset.
       edge = 1 if maximum is at edge of correlation domain, otherwise=0.
       plateau = 1 if maximum is in a plateua of correlation function, else=0.

       Find point of maximum cross-correlation and calc. corresponding offsets.
       If MAGNIFICATION > 1:
       the  correl_mat is checked for plateau near maximum, and if found,
       the center of plateau is taken as point of maximum cross-correlation.

       Written, July-1991, Frank Varosi, STX @ NASA/GSFC
       Use ROUND instead of NINT, June 1995 Wayne Landsman HSTX
       Remove use of non-standard !DEBUG system variable   W.L. HSTX
       Converted to IDL V5.0   W. Landsman   September 1997

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